chore: support MCP schema 2025-06-18 (#1621)

This updates the schema in `generate_mcp_types.py` from `2025-03-26` to
`2025-06-18`, regenerates `mcp-types/src/lib.rs`, and then updates all
the code that uses `mcp-types` to honor the changes.

Ran

```
npx @modelcontextprotocol/inspector just codex mcp
```

and verified that I was able to invoke the `codex` tool, as expected.


---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/1621).
* #1623
* #1622
* __->__ #1621

codex-rs/core/src/codex.rs

@@ -967,15 +967,17 @@ async fn run_task(sess: Arc<Session>, sub_id: String, input: Vec<InputItem>) {
                         ) => {
                             items_to_record_in_conversation_history.push(item);
                             let (content, success): (String, Option<bool>) = match result {
-                                Ok(CallToolResult { content, is_error }) => {
+                                Ok(CallToolResult {
-                                    match serde_json::to_string(content) {
+                                    content,
-                                        Ok(content) => (content, *is_error),
+                                    is_error,
-                                        Err(e) => {
+                                    structured_content: _,
-                                            warn!("Failed to serialize MCP tool call output: {e}");
+                                }) => match serde_json::to_string(content) {
-                                            (e.to_string(), Some(true))
+                                    Ok(content) => (content, *is_error),
-                                        }
+                                    Err(e) => {
+                                        warn!("Failed to serialize MCP tool call output: {e}");
+                                        (e.to_string(), Some(true))
                                     }
-                                }
+                                },
                                 Err(e) => (e.clone(), Some(true)),
                             };
                             items_to_record_in_conversation_history.push(
@@ -1353,7 +1355,7 @@ async fn handle_function_call(
             let params = match parse_container_exec_arguments(arguments, sess, &call_id) {
                 Ok(params) => params,
                 Err(output) => {
-                    return output;
+                    return *output;
                 }
             };
             handle_container_exec_with_params(params, sess, sub_id, call_id).await
@@ -1396,7 +1398,7 @@ fn parse_container_exec_arguments(
     arguments: String,
     sess: &Session,
     call_id: &str,
-) -> Result<ExecParams, ResponseInputItem> {
+) -> Result<ExecParams, Box<ResponseInputItem>> {
     // parse command
     match serde_json::from_str::<ShellToolCallParams>(&arguments) {
         Ok(shell_tool_call_params) => Ok(to_exec_params(shell_tool_call_params, sess)),
@@ -1409,7 +1411,7 @@ fn parse_container_exec_arguments(
                     success: None,
                 },
             };
-            Err(output)
+            Err(Box::new(output))
         }
     }
 }

codex-rs/core/src/mcp_connection_manager.rs

@@ -135,10 +135,12 @@ impl McpConnectionManager {
                                 experimental: None,
                                 roots: None,
                                 sampling: None,
+                                elicitation: None,
                             },
                             client_info: Implementation {
                                 name: "codex-mcp-client".to_owned(),
                                 version: env!("CARGO_PKG_VERSION").to_owned(),
+                                title: Some("Codex".into()),
                             },
                             protocol_version: mcp_types::MCP_SCHEMA_VERSION.to_owned(),
                         };
@@ -288,6 +290,8 @@ mod tests {
                     r#type: "object".to_string(),
                 },
                 name: tool_name.to_string(),
+                output_schema: None,
+                title: None,
             },
         }
     }

codex-rs/mcp-client/src/main.rs

@@ -57,10 +57,12 @@ async fn main() -> Result<()> {
             experimental: None,
             roots: None,
             sampling: None,
+            elicitation: None,
         },
         client_info: Implementation {
             name: "codex-mcp-client".to_owned(),
             version: env!("CARGO_PKG_VERSION").to_owned(),
+            title: Some("Codex".to_string()),
         },
         protocol_version: MCP_SCHEMA_VERSION.to_owned(),
     };

codex-rs/mcp-server/src/codex_tool_config.rs

@@ -108,7 +108,10 @@ pub(crate) fn create_tool_for_codex_tool_call_param() -> Tool {
 
     Tool {
         name: "codex".to_string(),
+        title: Some("Codex".to_string()),
         input_schema: tool_input_schema,
+        // TODO(mbolin): This should be defined.
+        output_schema: None,
         description: Some(
             "Run a Codex session. Accepts configuration parameters matching the Codex Config struct.".to_string(),
         ),
@@ -179,6 +182,7 @@ mod tests {
         let tool_json = serde_json::to_value(&tool).expect("tool serializes");
         let expected_tool_json = serde_json::json!({
           "name": "codex",
+          "title": "Codex",
           "description": "Run a Codex session. Accepts configuration parameters matching the Codex Config struct.",
           "inputSchema": {
             "type": "object",

codex-rs/mcp-server/src/codex_tool_runner.rs

@@ -12,7 +12,7 @@ use codex_core::protocol::Op;
 use codex_core::protocol::Submission;
 use codex_core::protocol::TaskCompleteEvent;
 use mcp_types::CallToolResult;
-use mcp_types::CallToolResultContent;
+use mcp_types::ContentBlock;
 use mcp_types::JSONRPC_VERSION;
 use mcp_types::JSONRPCMessage;
 use mcp_types::JSONRPCResponse;
@@ -44,12 +44,13 @@ pub async fn run_codex_tool_session(
         Ok(res) => res,
         Err(e) => {
             let result = CallToolResult {
-                content: vec![CallToolResultContent::TextContent(TextContent {
+                content: vec![ContentBlock::TextContent(TextContent {
                     r#type: "text".to_string(),
                     text: format!("Failed to start Codex session: {e}"),
                     annotations: None,
                 })],
                 is_error: Some(true),
+                structured_content: None,
             };
             let _ = outgoing
                 .send(JSONRPCMessage::Response(JSONRPCResponse {
@@ -88,8 +89,6 @@ pub async fn run_codex_tool_session(
         tracing::error!("Failed to submit initial prompt: {e}");
     }
 
-    let mut last_agent_message: Option<String> = None;
-
     // Stream events until the task needs to pause for user interaction or
     // completes.
     loop {
@@ -98,17 +97,15 @@ pub async fn run_codex_tool_session(
                 let _ = outgoing.send(codex_event_to_notification(&event)).await;
 
                 match &event.msg {
-                    EventMsg::AgentMessage(AgentMessageEvent { message }) => {
-                        last_agent_message = Some(message.clone());
-                    }
                     EventMsg::ExecApprovalRequest(_) => {
                         let result = CallToolResult {
-                            content: vec![CallToolResultContent::TextContent(TextContent {
+                            content: vec![ContentBlock::TextContent(TextContent {
                                 r#type: "text".to_string(),
                                 text: "EXEC_APPROVAL_REQUIRED".to_string(),
                                 annotations: None,
                             })],
                             is_error: None,
+                            structured_content: None,
                         };
                         let _ = outgoing
                             .send(JSONRPCMessage::Response(JSONRPCResponse {
@@ -121,12 +118,13 @@ pub async fn run_codex_tool_session(
                     }
                     EventMsg::ApplyPatchApprovalRequest(_) => {
                         let result = CallToolResult {
-                            content: vec![CallToolResultContent::TextContent(TextContent {
+                            content: vec![ContentBlock::TextContent(TextContent {
                                 r#type: "text".to_string(),
                                 text: "PATCH_APPROVAL_REQUIRED".to_string(),
                                 annotations: None,
                             })],
                             is_error: None,
+                            structured_content: None,
                         };
                         let _ = outgoing
                             .send(JSONRPCMessage::Response(JSONRPCResponse {
@@ -137,27 +135,19 @@ pub async fn run_codex_tool_session(
                             .await;
                         break;
                     }
-                    EventMsg::TaskComplete(TaskCompleteEvent {
+                    EventMsg::TaskComplete(TaskCompleteEvent { last_agent_message }) => {
-                        last_agent_message: _,
+                        let text = match last_agent_message {
-                    }) => {
+                            Some(msg) => msg.clone(),
-                        let result = if let Some(msg) = last_agent_message {
+                            None => "".to_string(),
-                            CallToolResult {
+                        };
-                                content: vec![CallToolResultContent::TextContent(TextContent {
+                        let result = CallToolResult {
-                                    r#type: "text".to_string(),
+                            content: vec![ContentBlock::TextContent(TextContent {
-                                    text: msg,
+                                r#type: "text".to_string(),
-                                    annotations: None,
+                                text,
-                                })],
+                                annotations: None,
-                                is_error: None,
+                            })],
-                            }
+                            is_error: None,
-                        } else {
+                            structured_content: None,
-                            CallToolResult {
-                                content: vec![CallToolResultContent::TextContent(TextContent {
-                                    r#type: "text".to_string(),
-                                    text: String::new(),
-                                    annotations: None,
-                                })],
-                                is_error: None,
-                            }
                         };
                         let _ = outgoing
                             .send(JSONRPCMessage::Response(JSONRPCResponse {
@@ -177,6 +167,9 @@ pub async fn run_codex_tool_session(
                     EventMsg::AgentReasoningDelta(_) => {
                         // TODO: think how we want to support this in the MCP
                     }
+                    EventMsg::AgentMessage(AgentMessageEvent { .. }) => {
+                        // TODO: think how we want to support this in the MCP
+                    }
                     EventMsg::Error(_)
                     | EventMsg::TaskStarted
                     | EventMsg::TokenCount(_)
@@ -200,12 +193,15 @@ pub async fn run_codex_tool_session(
             }
             Err(e) => {
                 let result = CallToolResult {
-                    content: vec![CallToolResultContent::TextContent(TextContent {
+                    content: vec![ContentBlock::TextContent(TextContent {
                         r#type: "text".to_string(),
                         text: format!("Codex runtime error: {e}"),
                         annotations: None,
                     })],
                     is_error: Some(true),
+                    // TODO(mbolin): Could present the error in a more
+                    // structured way.
+                    structured_content: None,
                 };
                 let _ = outgoing
                     .send(JSONRPCMessage::Response(JSONRPCResponse {

codex-rs/mcp-server/src/lib.rs

@@ -70,9 +70,7 @@ pub async fn run_main(codex_linux_sandbox_exe: Option<PathBuf>) -> IoResult<()>
                     JSONRPCMessage::Request(r) => processor.process_request(r),
                     JSONRPCMessage::Response(r) => processor.process_response(r),
                     JSONRPCMessage::Notification(n) => processor.process_notification(n),
-                    JSONRPCMessage::BatchRequest(b) => processor.process_batch_request(b),
                     JSONRPCMessage::Error(e) => processor.process_error(e),
-                    JSONRPCMessage::BatchResponse(b) => processor.process_batch_response(b),
                 }
             }
 

codex-rs/mcp-server/src/message_processor.rs

@@ -6,11 +6,9 @@ use crate::codex_tool_config::create_tool_for_codex_tool_call_param;
 use codex_core::config::Config as CodexConfig;
 use mcp_types::CallToolRequestParams;
 use mcp_types::CallToolResult;
-use mcp_types::CallToolResultContent;
 use mcp_types::ClientRequest;
+use mcp_types::ContentBlock;
 use mcp_types::JSONRPC_VERSION;
-use mcp_types::JSONRPCBatchRequest;
-use mcp_types::JSONRPCBatchResponse;
 use mcp_types::JSONRPCError;
 use mcp_types::JSONRPCErrorError;
 use mcp_types::JSONRPCMessage;
@@ -145,41 +143,11 @@ impl MessageProcessor {
         }
     }
 
-    /// Handle a batch of requests and/or notifications.
-    pub(crate) fn process_batch_request(&mut self, batch: JSONRPCBatchRequest) {
-        tracing::info!("<- batch request containing {} item(s)", batch.len());
-        for item in batch {
-            match item {
-                mcp_types::JSONRPCBatchRequestItem::JSONRPCRequest(req) => {
-                    self.process_request(req);
-                }
-                mcp_types::JSONRPCBatchRequestItem::JSONRPCNotification(note) => {
-                    self.process_notification(note);
-                }
-            }
-        }
-    }
-
     /// Handle an error object received from the peer.
     pub(crate) fn process_error(&mut self, err: JSONRPCError) {
         tracing::error!("<- error: {:?}", err);
     }
 
-    /// Handle a batch of responses/errors.
-    pub(crate) fn process_batch_response(&mut self, batch: JSONRPCBatchResponse) {
-        tracing::info!("<- batch response containing {} item(s)", batch.len());
-        for item in batch {
-            match item {
-                mcp_types::JSONRPCBatchResponseItem::JSONRPCResponse(resp) => {
-                    self.process_response(resp);
-                }
-                mcp_types::JSONRPCBatchResponseItem::JSONRPCError(err) => {
-                    self.process_error(err);
-                }
-            }
-        }
-    }
-
     fn handle_initialize(
         &mut self,
         id: RequestId,
@@ -224,6 +192,7 @@ impl MessageProcessor {
             server_info: mcp_types::Implementation {
                 name: "codex-mcp-server".to_string(),
                 version: mcp_types::MCP_SCHEMA_VERSION.to_string(),
+                title: Some("Codex".to_string()),
             },
         };
 
@@ -333,12 +302,13 @@ impl MessageProcessor {
         if name != "codex" {
             // Tool not found – return error result so the LLM can react.
             let result = CallToolResult {
-                content: vec![CallToolResultContent::TextContent(TextContent {
+                content: vec![ContentBlock::TextContent(TextContent {
                     r#type: "text".to_string(),
                     text: format!("Unknown tool '{name}'"),
                     annotations: None,
                 })],
                 is_error: Some(true),
+                structured_content: None,
             };
             self.send_response::<mcp_types::CallToolRequest>(id, result);
             return;
@@ -350,7 +320,7 @@ impl MessageProcessor {
                     Ok(cfg) => cfg,
                     Err(e) => {
                         let result = CallToolResult {
-                            content: vec![CallToolResultContent::TextContent(TextContent {
+                            content: vec![ContentBlock::TextContent(TextContent {
                                 r#type: "text".to_owned(),
                                 text: format!(
                                     "Failed to load Codex configuration from overrides: {e}"
@@ -358,6 +328,7 @@ impl MessageProcessor {
                                 annotations: None,
                             })],
                             is_error: Some(true),
+                            structured_content: None,
                         };
                         self.send_response::<mcp_types::CallToolRequest>(id, result);
                         return;
@@ -365,12 +336,13 @@ impl MessageProcessor {
                 },
                 Err(e) => {
                     let result = CallToolResult {
-                        content: vec![CallToolResultContent::TextContent(TextContent {
+                        content: vec![ContentBlock::TextContent(TextContent {
                             r#type: "text".to_owned(),
                             text: format!("Failed to parse configuration for Codex tool: {e}"),
                             annotations: None,
                         })],
                         is_error: Some(true),
+                        structured_content: None,
                     };
                     self.send_response::<mcp_types::CallToolRequest>(id, result);
                     return;
@@ -378,7 +350,7 @@ impl MessageProcessor {
             },
             None => {
                 let result = CallToolResult {
-                    content: vec![CallToolResultContent::TextContent(TextContent {
+                    content: vec![ContentBlock::TextContent(TextContent {
                         r#type: "text".to_string(),
                         text:
                             "Missing arguments for codex tool-call; the `prompt` field is required."
@@ -386,6 +358,7 @@ impl MessageProcessor {
                         annotations: None,
                     })],
                     is_error: Some(true),
+                    structured_content: None,
                 };
                 self.send_response::<mcp_types::CallToolRequest>(id, result);
                 return;
@@ -398,7 +371,7 @@ impl MessageProcessor {
         // Spawn an async task to handle the Codex session so that we do not
         // block the synchronous message-processing loop.
         task::spawn(async move {
-            // Run the Codex session and stream events back to the client.
+            // Run the Codex session and stream events Fck to the client.
             crate::codex_tool_runner::run_codex_tool_session(id, initial_prompt, config, outgoing)
                 .await;
         });

codex-rs/mcp-types/README.md

@@ -2,7 +2,7 @@
 
 Types for Model Context Protocol. Inspired by https://crates.io/crates/lsp-types.
 
-As documented on https://modelcontextprotocol.io/specification/2025-03-26/basic:
+As documented on https://modelcontextprotocol.io/specification/2025-06-18/basic:
 
-- TypeScript schema is the source of truth: https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-03-26/schema.ts
+- TypeScript schema is the source of truth: https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-06-18/schema.ts
-- JSON schema is amenable to automated tooling: https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-03-26/schema.json
+- JSON schema is amenable to automated tooling: https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/schema/2025-06-18/schema.json

codex-rs/mcp-types/generate_mcp_types.py

@@ -14,7 +14,7 @@ from pathlib import Path
 # Helper first so it is defined when other functions call it.
 from typing import Any, Literal
 
-SCHEMA_VERSION = "2025-03-26"
+SCHEMA_VERSION = "2025-06-18"
 JSONRPC_VERSION = "2.0"
 
 STANDARD_DERIVE = "#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]\n"
@@ -222,20 +222,7 @@ def add_definition(name: str, definition: dict[str, Any], out: list[str]) -> Non
     any_of = definition.get("anyOf", [])
     if any_of:
         assert isinstance(any_of, list)
-        if name == "JSONRPCMessage":
+        out.extend(define_any_of(name, any_of, description))
-            # Special case for JSONRPCMessage because its definition in the
-            # JSON schema does not quite match how we think about this type
-            # definition in Rust.
-            deep_copied_any_of = json.loads(json.dumps(any_of))
-            deep_copied_any_of[2] = {
-                "$ref": "#/definitions/JSONRPCBatchRequest",
-            }
-            deep_copied_any_of[5] = {
-                "$ref": "#/definitions/JSONRPCBatchResponse",
-            }
-            out.extend(define_any_of(name, deep_copied_any_of, description))
-        else:
-            out.extend(define_any_of(name, any_of, description))
         return
 
     type_prop = definition.get("type", None)
@@ -609,6 +596,8 @@ def rust_prop_name(name: str, is_optional: bool) -> RustProp:
         prop_name = "r#type"
     elif name == "ref":
         prop_name = "r#ref"
+    elif name == "enum":
+        prop_name = "r#enum"
     elif snake_case := to_snake_case(name):
         prop_name = snake_case
         is_rename = True

codex-rs/mcp-types/src/lib.rs

@@ -10,7 +10,7 @@ use serde::Serialize;
 use serde::de::DeserializeOwned;
 use std::convert::TryFrom;
 
-pub const MCP_SCHEMA_VERSION: &str = "2025-03-26";
+pub const MCP_SCHEMA_VERSION: &str = "2025-06-18";
 pub const JSONRPC_VERSION: &str = "2.0";
 
 /// Paired request/response types for the Model Context Protocol (MCP).
@@ -35,6 +35,12 @@ fn default_jsonrpc() -> String {
 pub struct Annotations {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub audience: Option<Vec<Role>>,
+    #[serde(
+        rename = "lastModified",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub last_modified: Option<String>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub priority: Option<f64>,
 }
@@ -50,6 +56,14 @@ pub struct AudioContent {
     pub r#type: String, // &'static str = "audio"
 }
 
+/// Base interface for metadata with name (identifier) and title (display name) properties.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct BaseMetadata {
+    pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct BlobResourceContents {
     pub blob: String,
@@ -58,6 +72,17 @@ pub struct BlobResourceContents {
     pub uri: String,
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct BooleanSchema {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub default: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    pub r#type: String, // &'static str = "boolean"
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum CallToolRequest {}
 
@@ -75,29 +100,17 @@ pub struct CallToolRequestParams {
 }
 
 /// The server's response to a tool call.
-///
-/// Any errors that originate from the tool SHOULD be reported inside the result
-/// object, with `isError` set to true, _not_ as an MCP protocol-level error
-/// response. Otherwise, the LLM would not be able to see that an error occurred
-/// and self-correct.
-///
-/// However, any errors in _finding_ the tool, an error indicating that the
-/// server does not support tool calls, or any other exceptional conditions,
-/// should be reported as an MCP error response.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CallToolResult {
-    pub content: Vec<CallToolResultContent>,
+    pub content: Vec<ContentBlock>,
     #[serde(rename = "isError", default, skip_serializing_if = "Option::is_none")]
     pub is_error: Option<bool>,
-}
+    #[serde(
-
+        rename = "structuredContent",
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+        default,
-#[serde(untagged)]
+        skip_serializing_if = "Option::is_none"
-pub enum CallToolResultContent {
+    )]
-    TextContent(TextContent),
+    pub structured_content: Option<serde_json::Value>,
-    ImageContent(ImageContent),
-    AudioContent(AudioContent),
-    EmbeddedResource(EmbeddedResource),
 }
 
 impl From<CallToolResult> for serde_json::Value {
@@ -127,6 +140,8 @@ pub struct CancelledNotificationParams {
 /// Capabilities a client may support. Known capabilities are defined here, in this schema, but this is not a closed set: any client can define its own, additional capabilities.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ClientCapabilities {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub elicitation: Option<serde_json::Value>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub experimental: Option<serde_json::Value>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
@@ -194,6 +209,7 @@ pub enum ClientResult {
     Result(Result),
     CreateMessageResult(CreateMessageResult),
     ListRootsResult(ListRootsResult),
+    ElicitResult(ElicitResult),
 }
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
@@ -208,9 +224,18 @@ impl ModelContextProtocolRequest for CompleteRequest {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CompleteRequestParams {
     pub argument: CompleteRequestParamsArgument,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub context: Option<CompleteRequestParamsContext>,
     pub r#ref: CompleteRequestParamsRef,
 }
 
+/// Additional, optional context for completions
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct CompleteRequestParamsContext {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub arguments: Option<serde_json::Value>,
+}
+
 /// The argument's information
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CompleteRequestParamsArgument {
@@ -222,7 +247,7 @@ pub struct CompleteRequestParamsArgument {
 #[serde(untagged)]
 pub enum CompleteRequestParamsRef {
     PromptReference(PromptReference),
-    ResourceReference(ResourceReference),
+    ResourceTemplateReference(ResourceTemplateReference),
 }
 
 /// The server's response to a completion/complete request
@@ -248,6 +273,16 @@ impl From<CompleteResult> for serde_json::Value {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+#[serde(untagged)]
+pub enum ContentBlock {
+    TextContent(TextContent),
+    ImageContent(ImageContent),
+    AudioContent(AudioContent),
+    ResourceLink(ResourceLink),
+    EmbeddedResource(EmbeddedResource),
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum CreateMessageRequest {}
 
@@ -325,6 +360,48 @@ impl From<CreateMessageResult> for serde_json::Value {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Cursor(String);
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub enum ElicitRequest {}
+
+impl ModelContextProtocolRequest for ElicitRequest {
+    const METHOD: &'static str = "elicitation/create";
+    type Params = ElicitRequestParams;
+    type Result = ElicitResult;
+}
+
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ElicitRequestParams {
+    pub message: String,
+    #[serde(rename = "requestedSchema")]
+    pub requested_schema: ElicitRequestParamsRequestedSchema,
+}
+
+/// A restricted subset of JSON Schema.
+/// Only top-level properties are allowed, without nesting.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ElicitRequestParamsRequestedSchema {
+    pub properties: serde_json::Value,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub required: Option<Vec<String>>,
+    pub r#type: String, // &'static str = "object"
+}
+
+/// The client's response to an elicitation request.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ElicitResult {
+    pub action: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub content: Option<serde_json::Value>,
+}
+
+impl From<ElicitResult> for serde_json::Value {
+    fn from(value: ElicitResult) -> Self {
+        // Leave this as it should never fail
+        #[expect(clippy::unwrap_used)]
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 /// The contents of a resource, embedded into a prompt or tool call result.
 ///
 /// It is up to the client how best to render embedded resources for the benefit
@@ -346,6 +423,18 @@ pub enum EmbeddedResourceResource {
 
 pub type EmptyResult = Result;
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct EnumSchema {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    pub r#enum: Vec<String>,
+    #[serde(rename = "enumNames", default, skip_serializing_if = "Option::is_none")]
+    pub enum_names: Option<Vec<String>>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    pub r#type: String, // &'static str = "string"
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum GetPromptRequest {}
 
@@ -389,10 +478,12 @@ pub struct ImageContent {
     pub r#type: String, // &'static str = "image"
 }
 
-/// Describes the name and version of an MCP implementation.
+/// Describes the name and version of an MCP implementation, with an optional title for UI representation.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Implementation {
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
     pub version: String,
 }
 
@@ -442,24 +533,6 @@ impl ModelContextProtocolNotification for InitializedNotification {
     type Params = Option<serde_json::Value>;
 }
 
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
-#[serde(untagged)]
-pub enum JSONRPCBatchRequestItem {
-    JSONRPCRequest(JSONRPCRequest),
-    JSONRPCNotification(JSONRPCNotification),
-}
-
-pub type JSONRPCBatchRequest = Vec<JSONRPCBatchRequestItem>;
-
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
-#[serde(untagged)]
-pub enum JSONRPCBatchResponseItem {
-    JSONRPCResponse(JSONRPCResponse),
-    JSONRPCError(JSONRPCError),
-}
-
-pub type JSONRPCBatchResponse = Vec<JSONRPCBatchResponseItem>;
-
 /// A response to a request that indicates an error occurred.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct JSONRPCError {
@@ -483,10 +556,8 @@ pub struct JSONRPCErrorError {
 pub enum JSONRPCMessage {
     Request(JSONRPCRequest),
     Notification(JSONRPCNotification),
-    BatchRequest(JSONRPCBatchRequest),
     Response(JSONRPCResponse),
     Error(JSONRPCError),
-    BatchResponse(JSONRPCBatchResponse),
 }
 
 /// A notification which does not expect a response.
@@ -777,6 +848,19 @@ pub struct Notification {
     pub params: Option<serde_json::Value>,
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct NumberSchema {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub maximum: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub minimum: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    pub r#type: String,
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PaginatedRequest {
     pub method: String,
@@ -817,6 +901,17 @@ impl ModelContextProtocolRequest for PingRequest {
     type Result = Result;
 }
 
+/// Restricted schema definitions that only allow primitive types
+/// without nested objects or arrays.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+#[serde(untagged)]
+pub enum PrimitiveSchemaDefinition {
+    StringSchema(StringSchema),
+    NumberSchema(NumberSchema),
+    BooleanSchema(BooleanSchema),
+    EnumSchema(EnumSchema),
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ProgressNotification {}
 
@@ -851,6 +946,8 @@ pub struct Prompt {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub description: Option<String>,
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
 }
 
 /// Describes an argument that a prompt can accept.
@@ -861,6 +958,8 @@ pub struct PromptArgument {
     pub name: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub required: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
 }
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
@@ -877,23 +976,16 @@ impl ModelContextProtocolNotification for PromptListChangedNotification {
 /// resources from the MCP server.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PromptMessage {
-    pub content: PromptMessageContent,
+    pub content: ContentBlock,
     pub role: Role,
 }
 
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
-#[serde(untagged)]
-pub enum PromptMessageContent {
-    TextContent(TextContent),
-    ImageContent(ImageContent),
-    AudioContent(AudioContent),
-    EmbeddedResource(EmbeddedResource),
-}
-
 /// Identifies a prompt.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PromptReference {
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
     pub r#type: String, // &'static str = "ref/prompt"
 }
 
@@ -958,6 +1050,8 @@ pub struct Resource {
     pub name: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub size: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
     pub uri: String,
 }
 
@@ -969,6 +1063,26 @@ pub struct ResourceContents {
     pub uri: String,
 }
 
+/// A resource that the server is capable of reading, included in a prompt or tool call result.
+///
+/// Note: resource links returned by tools are not guaranteed to appear in the results of `resources/list` requests.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ResourceLink {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub annotations: Option<Annotations>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
+    pub mime_type: Option<String>,
+    pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub size: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    pub r#type: String, // &'static str = "resource_link"
+    pub uri: String,
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ResourceListChangedNotification {}
 
@@ -977,13 +1091,6 @@ impl ModelContextProtocolNotification for ResourceListChangedNotification {
     type Params = Option<serde_json::Value>;
 }
 
-/// A reference to a resource or resource template definition.
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
-pub struct ResourceReference {
-    pub r#type: String, // &'static str = "ref/resource"
-    pub uri: String,
-}
-
 /// A template description for resources available on the server.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ResourceTemplate {
@@ -994,10 +1101,19 @@ pub struct ResourceTemplate {
     #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
     pub mime_type: Option<String>,
     pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
     #[serde(rename = "uriTemplate")]
     pub uri_template: String,
 }
 
+/// A reference to a resource or resource template definition.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ResourceTemplateReference {
+    pub r#type: String, // &'static str = "ref/resource"
+    pub uri: String,
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ResourceUpdatedNotification {}
 
@@ -1140,6 +1256,7 @@ pub enum ServerRequest {
     PingRequest(PingRequest),
     CreateMessageRequest(CreateMessageRequest),
     ListRootsRequest(ListRootsRequest),
+    ElicitRequest(ElicitRequest),
 }
 
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
@@ -1172,6 +1289,21 @@ pub struct SetLevelRequestParams {
     pub level: LoggingLevel,
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct StringSchema {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub format: Option<String>,
+    #[serde(rename = "maxLength", default, skip_serializing_if = "Option::is_none")]
+    pub max_length: Option<i64>,
+    #[serde(rename = "minLength", default, skip_serializing_if = "Option::is_none")]
+    pub min_length: Option<i64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+    pub r#type: String, // &'static str = "string"
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum SubscribeRequest {}
 
@@ -1213,6 +1345,25 @@ pub struct Tool {
     #[serde(rename = "inputSchema")]
     pub input_schema: ToolInputSchema,
     pub name: String,
+    #[serde(
+        rename = "outputSchema",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub output_schema: Option<ToolOutputSchema>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub title: Option<String>,
+}
+
+/// An optional JSON Schema object defining the structure of the tool's output returned in
+/// the structuredContent field of a CallToolResult.
+#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
+pub struct ToolOutputSchema {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub properties: Option<serde_json::Value>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub required: Option<Vec<String>>,
+    pub r#type: String, // &'static str = "object"
 }
 
 /// A JSON Schema object defining the expected parameters for the tool.

codex-rs/mcp-types/tests/initialize.rs

@@ -17,8 +17,8 @@ fn deserialize_initialize_request() {
         "method": "initialize",
         "params": {
             "capabilities": {},
-            "clientInfo": { "name": "acme-client", "version": "1.2.3" },
+            "clientInfo": { "name": "acme-client", "title": "Acme", "version": "1.2.3" },
-            "protocolVersion": "2025-03-26"
+            "protocolVersion": "2025-06-18"
         }
     }"#;
 
@@ -37,8 +37,8 @@ fn deserialize_initialize_request() {
         method: "initialize".into(),
         params: Some(json!({
             "capabilities": {},
-            "clientInfo": { "name": "acme-client", "version": "1.2.3" },
+            "clientInfo": { "name": "acme-client", "title": "Acme", "version": "1.2.3" },
-            "protocolVersion": "2025-03-26"
+            "protocolVersion": "2025-06-18"
         })),
     };
 
@@ -57,12 +57,14 @@ fn deserialize_initialize_request() {
                 experimental: None,
                 roots: None,
                 sampling: None,
+                elicitation: None,
             },
             client_info: Implementation {
                 name: "acme-client".into(),
+                title: Some("Acme".to_string()),
                 version: "1.2.3".into(),
             },
-            protocol_version: "2025-03-26".into(),
+            protocol_version: "2025-06-18".into(),
         }
     );
 }

codex-rs/tui/src/history_cell.rs

@@ -17,6 +17,7 @@ use image::GenericImageView;
 use image::ImageReader;
 use lazy_static::lazy_static;
 use mcp_types::EmbeddedResourceResource;
+use mcp_types::ResourceLink;
 use ratatui::prelude::*;
 use ratatui::style::Color;
 use ratatui::style::Modifier;
@@ -331,8 +332,7 @@ impl HistoryCell {
     ) -> Option<Self> {
         match result {
             Ok(mcp_types::CallToolResult { content, .. }) => {
-                if let Some(mcp_types::CallToolResultContent::ImageContent(image)) = content.first()
+                if let Some(mcp_types::ContentBlock::ImageContent(image)) = content.first() {
-                {
                     let raw_data =
                         match base64::engine::general_purpose::STANDARD.decode(&image.data) {
                             Ok(data) => data,
@@ -405,21 +405,21 @@ impl HistoryCell {
 
                     for tool_call_result in content {
                         let line_text = match tool_call_result {
-                            mcp_types::CallToolResultContent::TextContent(text) => {
+                            mcp_types::ContentBlock::TextContent(text) => {
                                 format_and_truncate_tool_result(
                                     &text.text,
                                     TOOL_CALL_MAX_LINES,
                                     num_cols as usize,
                                 )
                             }
-                            mcp_types::CallToolResultContent::ImageContent(_) => {
+                            mcp_types::ContentBlock::ImageContent(_) => {
                                 // TODO show images even if they're not the first result, will require a refactor of `CompletedMcpToolCall`
                                 "<image content>".to_string()
                             }
-                            mcp_types::CallToolResultContent::AudioContent(_) => {
+                            mcp_types::ContentBlock::AudioContent(_) => {
                                 "<audio content>".to_string()
                             }
-                            mcp_types::CallToolResultContent::EmbeddedResource(resource) => {
+                            mcp_types::ContentBlock::EmbeddedResource(resource) => {
                                 let uri = match resource.resource {
                                     EmbeddedResourceResource::TextResourceContents(text) => {
                                         text.uri
@@ -430,6 +430,9 @@ impl HistoryCell {
                                 };
                                 format!("embedded resource: {uri}")
                             }
+                            mcp_types::ContentBlock::ResourceLink(ResourceLink { uri, .. }) => {
+                                format!("link: {uri}")
+                            }
                         };
                         lines.push(Line::styled(line_text, Style::default().fg(Color::Gray)));
                     }