MCP server: route structured tool-call requests and expose mcp_protocol [Stack 2/3] (#1751)

- Expose mcp_protocol from mcp-server for reuse in tests and callers.
- In MessageProcessor, detect structured ToolCallRequestParams in
tools/call and forward to a new handler.
- Add handle_new_tool_calls scaffold (returns error for now).
- Test helper: add send_send_user_message_tool_call to McpProcess to
send ConversationSendMessage requests;

This is the second PR in a stack.
Stack:
Final: #1686
Intermediate: #1751
First: #1750

codex-rs/Cargo.lock

@@ -2643,6 +2643,7 @@ version = "0.0.0"
 dependencies = [
  "anyhow",
  "assert_cmd",
+ "codex-core",
  "codex-mcp-server",
  "mcp-types",
  "pretty_assertions",
@@ -2650,6 +2651,7 @@ dependencies = [
  "shlex",
  "tempfile",
  "tokio",
+ "uuid",
  "wiremock",
 ]
 

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

@@ -19,7 +19,7 @@ mod codex_tool_config;
 mod codex_tool_runner;
 mod exec_approval;
 mod json_to_toml;
-mod mcp_protocol;
+pub mod mcp_protocol;
 mod message_processor;
 mod outgoing_message;
 mod patch_approval;

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

@@ -6,6 +6,7 @@ use crate::codex_tool_config::CodexToolCallParam;
 use crate::codex_tool_config::CodexToolCallReplyParam;
 use crate::codex_tool_config::create_tool_for_codex_tool_call_param;
 use crate::codex_tool_config::create_tool_for_codex_tool_call_reply_param;
+use crate::mcp_protocol::ToolCallRequestParams;
 use crate::outgoing_message::OutgoingMessageSender;
 
 use codex_core::Codex;
@@ -300,6 +301,14 @@ impl MessageProcessor {
         params: <mcp_types::CallToolRequest as mcp_types::ModelContextProtocolRequest>::Params,
     ) {
         tracing::info!("tools/call -> params: {:?}", params);
+        // Serialize params into JSON and try to parse as new type
+        if let Ok(new_params) =
+            serde_json::to_value(&params).and_then(serde_json::from_value::<ToolCallRequestParams>)
+        {
+            // New tool call matched → forward
+            self.handle_new_tool_calls(id, new_params).await;
+            return;
+        }
         let CallToolRequestParams { name, arguments } = params;
 
         match name.as_str() {
@@ -323,6 +332,20 @@ impl MessageProcessor {
             }
         }
     }
+    async fn handle_new_tool_calls(&self, request_id: RequestId, _params: ToolCallRequestParams) {
+        // TODO: implement the new tool calls
+        let result = CallToolResult {
+            content: vec![ContentBlock::TextContent(TextContent {
+                r#type: "text".to_string(),
+                text: "Unknown tool".to_string(),
+                annotations: None,
+            })],
+            is_error: Some(true),
+            structured_content: None,
+        };
+        self.send_response::<mcp_types::CallToolRequest>(request_id, result)
+            .await;
+    }
 
     async fn handle_tool_call_codex(&self, id: RequestId, arguments: Option<serde_json::Value>) {
         let (initial_prompt, config): (String, CodexConfig) = match arguments {

codex-rs/mcp-server/tests/common/Cargo.toml

@@ -10,6 +10,7 @@ path = "lib.rs"
 anyhow = "1"
 assert_cmd = "2"
 codex-mcp-server = { path = "../.." }
+codex-core = { path = "../../../core" }
 mcp-types = { path = "../../../mcp-types" }
 pretty_assertions = "1.4.1"
 serde_json = "1"
@@ -22,3 +23,4 @@ tokio = { version = "1", features = [
     "rt-multi-thread",
 ] }
 wiremock = "0.6"
+uuid = { version = "1", features = ["serde", "v4"] }

codex-rs/mcp-server/tests/common/mcp_process.rs

@@ -11,8 +11,13 @@ use tokio::process::ChildStdout;
 
 use anyhow::Context;
 use assert_cmd::prelude::*;
+use codex_core::protocol::InputItem;
 use codex_mcp_server::CodexToolCallParam;
 use codex_mcp_server::CodexToolCallReplyParam;
+use codex_mcp_server::mcp_protocol::ConversationId;
+use codex_mcp_server::mcp_protocol::ConversationSendMessageArgs;
+use codex_mcp_server::mcp_protocol::ToolCallRequestParams;
+
 use mcp_types::CallToolRequestParams;
 use mcp_types::ClientCapabilities;
 use mcp_types::Implementation;
@@ -29,6 +34,7 @@ use pretty_assertions::assert_eq;
 use serde_json::json;
 use std::process::Command as StdCommand;
 use tokio::process::Command;
+use uuid::Uuid;
 
 pub struct McpProcess {
     next_request_id: AtomicI64,
@@ -174,6 +180,26 @@ impl McpProcess {
         .await
     }
 
+    pub async fn send_user_message_tool_call(
+        &mut self,
+        message: &str,
+        session_id: &str,
+    ) -> anyhow::Result<i64> {
+        let params = ToolCallRequestParams::ConversationSendMessage(ConversationSendMessageArgs {
+            conversation_id: ConversationId(Uuid::parse_str(session_id)?),
+            content: vec![InputItem::Text {
+                text: message.to_string(),
+            }],
+            parent_message_id: None,
+            conversation_overrides: None,
+        });
+        self.send_request(
+            mcp_types::CallToolRequest::METHOD,
+            Some(serde_json::to_value(params)?),
+        )
+        .await
+    }
+
     async fn send_request(
         &mut self,
         method: &str,