fix: mcp-types serialization wasn't quite working (#791)

While creating a basic MCP server in https://github.com/openai/codex/pull/792, I discovered a number of bugs with the initial `mcp-types` crate that I needed to fix in order to implement the server. For example, I discovered that when serializing a message, `"jsonrpc": "2.0"` was not being included. I changed the codegen so that the field is added as: ```rust #[serde(rename = "jsonrpc", default = "default_jsonrpc")] pub jsonrpc: String, ``` This ensures that the field is serialized as `"2.0"`, though the field still has to be assigned, which is tedious. I may experiment with `Default` or something else in the future. (I also considered creating a custom serializer, but I'm not sure it's worth the trouble.) While here, I also added `MCP_SCHEMA_VERSION` and `JSONRPC_VERSION` as `pub const`s for the crate. I also discovered that MCP rejects sending `null` for optional fields, so I had to add `#[serde(skip_serializing_if = "Option::is_none")]` on `Option` fields. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/openai/codex/pull/791). * #792 * __->__ #791
2025-05-02 16:38:05 -07:00
parent 83961e0299
commit 865e518771
3 changed files with 316 additions and 47 deletions
--- a/codex-rs/mcp-types/src/lib.rs
+++ b/codex-rs/mcp-types/src/lib.rs
@@ -10,6 +10,9 @@ use serde::Deserialize;
 use serde::Serialize;
 use std::convert::TryFrom;

+pub const MCP_SCHEMA_VERSION: &str = "2025-03-26";
+pub const JSONRPC_VERSION: &str = "2.0";
+
 /// Paired request/response types for the Model Context Protocol (MCP).
 pub trait ModelContextProtocolRequest {
    const METHOD: &'static str;
@@ -23,16 +26,23 @@ pub trait ModelContextProtocolNotification {
    type Params: DeserializeOwned + Serialize + Send + Sync + 'static;
 }

+fn default_jsonrpc() -> String {
+    JSONRPC_VERSION.to_owned()
+}
+
 /// Optional annotations for the client. The client can use annotations to inform how objects are used or displayed
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Annotations {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub audience: Option<Vec<Role>>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub priority: Option<f64>,
 }

 /// Audio provided to or from an LLM.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct AudioContent {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<Annotations>,
    pub data: String,
    #[serde(rename = "mimeType")]
@@ -43,7 +53,7 @@ pub struct AudioContent {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct BlobResourceContents {
    pub blob: String,
-    #[serde(rename = "mimeType")]
+    #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
    pub mime_type: Option<String>,
    pub uri: String,
 }
@@ -59,6 +69,7 @@ impl ModelContextProtocolRequest for CallToolRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CallToolRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub arguments: Option<serde_json::Value>,
    pub name: String,
 }
@@ -76,7 +87,7 @@ pub struct CallToolRequestParams {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CallToolResult {
    pub content: Vec<CallToolResultContent>,
-    #[serde(rename = "isError")]
+    #[serde(rename = "isError", default, skip_serializing_if = "Option::is_none")]
    pub is_error: Option<bool>,
 }

@@ -88,6 +99,12 @@ pub enum CallToolResultContent {
    EmbeddedResource(EmbeddedResource),
 }

+impl From<CallToolResult> for serde_json::Value {
+    fn from(value: CallToolResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum CancelledNotification {}

@@ -98,6 +115,7 @@ impl ModelContextProtocolNotification for CancelledNotification {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CancelledNotificationParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub reason: Option<String>,
    #[serde(rename = "requestId")]
    pub request_id: RequestId,
@@ -106,15 +124,22 @@ 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 experimental: Option<serde_json::Value>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub roots: Option<ClientCapabilitiesRoots>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub sampling: Option<serde_json::Value>,
 }

 /// Present if the client supports listing roots.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ClientCapabilitiesRoots {
-    #[serde(rename = "listChanged")]
+    #[serde(
+        rename = "listChanged",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub list_changed: Option<bool>,
 }

@@ -202,12 +227,19 @@ pub struct CompleteResult {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CompleteResultCompletion {
-    #[serde(rename = "hasMore")]
+    #[serde(rename = "hasMore", default, skip_serializing_if = "Option::is_none")]
    pub has_more: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub total: Option<i64>,
    pub values: Vec<String>,
 }

+impl From<CompleteResult> for serde_json::Value {
+    fn from(value: CompleteResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum CreateMessageRequest {}

@@ -219,18 +251,36 @@ impl ModelContextProtocolRequest for CreateMessageRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct CreateMessageRequestParams {
-    #[serde(rename = "includeContext")]
+    #[serde(
+        rename = "includeContext",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub include_context: Option<String>,
    #[serde(rename = "maxTokens")]
    pub max_tokens: i64,
    pub messages: Vec<SamplingMessage>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub metadata: Option<serde_json::Value>,
-    #[serde(rename = "modelPreferences")]
+    #[serde(
+        rename = "modelPreferences",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub model_preferences: Option<ModelPreferences>,
-    #[serde(rename = "stopSequences")]
+    #[serde(
+        rename = "stopSequences",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub stop_sequences: Option<Vec<String>>,
-    #[serde(rename = "systemPrompt")]
+    #[serde(
+        rename = "systemPrompt",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub system_prompt: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub temperature: Option<f64>,
 }

@@ -240,7 +290,11 @@ pub struct CreateMessageResult {
    pub content: CreateMessageResultContent,
    pub model: String,
    pub role: Role,
-    #[serde(rename = "stopReason")]
+    #[serde(
+        rename = "stopReason",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub stop_reason: Option<String>,
 }

@@ -251,6 +305,12 @@ pub enum CreateMessageResultContent {
    AudioContent(AudioContent),
 }

+impl From<CreateMessageResult> for serde_json::Value {
+    fn from(value: CreateMessageResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Cursor(String);

@@ -260,6 +320,7 @@ pub struct Cursor(String);
 /// of the LLM and/or the user.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct EmbeddedResource {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<Annotations>,
    pub resource: EmbeddedResourceResource,
    pub r#type: String, // &'static str = "resource"
@@ -284,6 +345,7 @@ impl ModelContextProtocolRequest for GetPromptRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct GetPromptRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub arguments: Option<serde_json::Value>,
    pub name: String,
 }
@@ -291,13 +353,21 @@ pub struct GetPromptRequestParams {
 /// The server's response to a prompts/get request from the client.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct GetPromptResult {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
    pub messages: Vec<PromptMessage>,
 }

+impl From<GetPromptResult> for serde_json::Value {
+    fn from(value: GetPromptResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 /// An image provided to or from an LLM.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ImageContent {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<Annotations>,
    pub data: String,
    #[serde(rename = "mimeType")]
@@ -334,6 +404,7 @@ pub struct InitializeRequestParams {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct InitializeResult {
    pub capabilities: ServerCapabilities,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub instructions: Option<String>,
    #[serde(rename = "protocolVersion")]
    pub protocol_version: String,
@@ -341,6 +412,12 @@ pub struct InitializeResult {
    pub server_info: Implementation,
 }

+impl From<InitializeResult> for serde_json::Value {
+    fn from(value: InitializeResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum InitializedNotification {}

@@ -370,11 +447,14 @@ pub type JSONRPCBatchResponse = Vec<JSONRPCBatchResponseItem>;
 pub struct JSONRPCError {
    pub error: JSONRPCErrorError,
    pub id: RequestId,
+    #[serde(rename = "jsonrpc", default = "default_jsonrpc")]
+    pub jsonrpc: String,
 }

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct JSONRPCErrorError {
    pub code: i64,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub data: Option<serde_json::Value>,
    pub message: String,
 }
@@ -394,7 +474,10 @@ pub enum JSONRPCMessage {
 /// A notification which does not expect a response.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct JSONRPCNotification {
+    #[serde(rename = "jsonrpc", default = "default_jsonrpc")]
+    pub jsonrpc: String,
    pub method: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub params: Option<serde_json::Value>,
 }

@@ -402,7 +485,10 @@ pub struct JSONRPCNotification {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct JSONRPCRequest {
    pub id: RequestId,
+    #[serde(rename = "jsonrpc", default = "default_jsonrpc")]
+    pub jsonrpc: String,
    pub method: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub params: Option<serde_json::Value>,
 }

@@ -410,6 +496,8 @@ pub struct JSONRPCRequest {
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct JSONRPCResponse {
    pub id: RequestId,
+    #[serde(rename = "jsonrpc", default = "default_jsonrpc")]
+    pub jsonrpc: String,
    pub result: Result,
 }

@@ -424,17 +512,28 @@ impl ModelContextProtocolRequest for ListPromptsRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListPromptsRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cursor: Option<String>,
 }

 /// The server's response to a prompts/list request from the client.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListPromptsResult {
-    #[serde(rename = "nextCursor")]
+    #[serde(
+        rename = "nextCursor",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub next_cursor: Option<String>,
    pub prompts: Vec<Prompt>,
 }

+impl From<ListPromptsResult> for serde_json::Value {
+    fn from(value: ListPromptsResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ListResourceTemplatesRequest {}

@@ -446,18 +545,29 @@ impl ModelContextProtocolRequest for ListResourceTemplatesRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListResourceTemplatesRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cursor: Option<String>,
 }

 /// The server's response to a resources/templates/list request from the client.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListResourceTemplatesResult {
-    #[serde(rename = "nextCursor")]
+    #[serde(
+        rename = "nextCursor",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub next_cursor: Option<String>,
    #[serde(rename = "resourceTemplates")]
    pub resource_templates: Vec<ResourceTemplate>,
 }

+impl From<ListResourceTemplatesResult> for serde_json::Value {
+    fn from(value: ListResourceTemplatesResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ListResourcesRequest {}

@@ -469,17 +579,28 @@ impl ModelContextProtocolRequest for ListResourcesRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListResourcesRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cursor: Option<String>,
 }

 /// The server's response to a resources/list request from the client.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListResourcesResult {
-    #[serde(rename = "nextCursor")]
+    #[serde(
+        rename = "nextCursor",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub next_cursor: Option<String>,
    pub resources: Vec<Resource>,
 }

+impl From<ListResourcesResult> for serde_json::Value {
+    fn from(value: ListResourcesResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ListRootsRequest {}

@@ -497,6 +618,12 @@ pub struct ListRootsResult {
    pub roots: Vec<Root>,
 }

+impl From<ListRootsResult> for serde_json::Value {
+    fn from(value: ListRootsResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum ListToolsRequest {}

@@ -508,17 +635,28 @@ impl ModelContextProtocolRequest for ListToolsRequest {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListToolsRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cursor: Option<String>,
 }

 /// The server's response to a tools/list request from the client.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ListToolsResult {
-    #[serde(rename = "nextCursor")]
+    #[serde(
+        rename = "nextCursor",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub next_cursor: Option<String>,
    pub tools: Vec<Tool>,
 }

+impl From<ListToolsResult> for serde_json::Value {
+    fn from(value: ListToolsResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 /// The severity of a log message.
 ///
 /// These map to syslog message severities, as specified in RFC-5424:
@@ -555,6 +693,7 @@ impl ModelContextProtocolNotification for LoggingMessageNotification {
 pub struct LoggingMessageNotificationParams {
    pub data: serde_json::Value,
    pub level: LoggingLevel,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub logger: Option<String>,
 }

@@ -564,6 +703,7 @@ pub struct LoggingMessageNotificationParams {
 /// to the client to interpret.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ModelHint {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub name: Option<String>,
 }

@@ -580,38 +720,64 @@ pub struct ModelHint {
 /// balance them against other considerations.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ModelPreferences {
-    #[serde(rename = "costPriority")]
+    #[serde(
+        rename = "costPriority",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub cost_priority: Option<f64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub hints: Option<Vec<ModelHint>>,
-    #[serde(rename = "intelligencePriority")]
+    #[serde(
+        rename = "intelligencePriority",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub intelligence_priority: Option<f64>,
-    #[serde(rename = "speedPriority")]
+    #[serde(
+        rename = "speedPriority",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub speed_priority: Option<f64>,
 }

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Notification {
    pub method: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub params: Option<serde_json::Value>,
 }

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PaginatedRequest {
    pub method: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub params: Option<PaginatedRequestParams>,
 }

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PaginatedRequestParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cursor: Option<String>,
 }

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PaginatedResult {
-    #[serde(rename = "nextCursor")]
+    #[serde(
+        rename = "nextCursor",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub next_cursor: Option<String>,
 }

+impl From<PaginatedResult> for serde_json::Value {
+    fn from(value: PaginatedResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub enum PingRequest {}

@@ -631,10 +797,12 @@ impl ModelContextProtocolNotification for ProgressNotification {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ProgressNotificationParams {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub message: Option<String>,
    pub progress: f64,
    #[serde(rename = "progressToken")]
    pub progress_token: ProgressToken,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub total: Option<f64>,
 }

@@ -648,7 +816,9 @@ pub enum ProgressToken {
 /// A prompt or prompt template that the server offers.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Prompt {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub arguments: Option<Vec<PromptArgument>>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
    pub name: String,
 }
@@ -656,8 +826,10 @@ pub struct Prompt {
 /// Describes an argument that a prompt can accept.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct PromptArgument {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
    pub name: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub required: Option<bool>,
 }

@@ -720,9 +892,16 @@ pub enum ReadResourceResultContents {
    BlobResourceContents(BlobResourceContents),
 }

+impl From<ReadResourceResult> for serde_json::Value {
+    fn from(value: ReadResourceResult) -> Self {
+        serde_json::to_value(value).unwrap()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Request {
    pub method: String,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub params: Option<serde_json::Value>,
 }

@@ -736,11 +915,14 @@ pub enum RequestId {
 /// A known resource that the server is capable of reading.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Resource {
+    #[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")]
+    #[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>,
    pub uri: String,
 }
@@ -748,7 +930,7 @@ pub struct Resource {
 /// The contents of a specific resource or sub-resource.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ResourceContents {
-    #[serde(rename = "mimeType")]
+    #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
    pub mime_type: Option<String>,
    pub uri: String,
 }
@@ -771,9 +953,11 @@ pub struct ResourceReference {
 /// A template description for resources available on the server.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ResourceTemplate {
+    #[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")]
+    #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
    pub mime_type: Option<String>,
    pub name: String,
    #[serde(rename = "uriTemplate")]
@@ -793,8 +977,7 @@ pub struct ResourceUpdatedNotificationParams {
    pub uri: String,
 }

-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
-pub struct Result {}
+pub type Result = serde_json::Value;

 /// The sender or recipient of messages and data in a conversation.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
@@ -808,6 +991,7 @@ pub enum Role {
 /// Represents a root directory or file that the server can operate on.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Root {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub name: Option<String>,
    pub uri: String,
 }
@@ -837,33 +1021,52 @@ pub enum SamplingMessageContent {
 /// Capabilities that a server may support. Known capabilities are defined here, in this schema, but this is not a closed set: any server can define its own, additional capabilities.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ServerCapabilities {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub completions: 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")]
    pub logging: Option<serde_json::Value>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub prompts: Option<ServerCapabilitiesPrompts>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub resources: Option<ServerCapabilitiesResources>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub tools: Option<ServerCapabilitiesTools>,
 }

 /// Present if the server offers any tools to call.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ServerCapabilitiesTools {
-    #[serde(rename = "listChanged")]
+    #[serde(
+        rename = "listChanged",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub list_changed: Option<bool>,
 }

 /// Present if the server offers any resources to read.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ServerCapabilitiesResources {
-    #[serde(rename = "listChanged")]
+    #[serde(
+        rename = "listChanged",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub list_changed: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub subscribe: Option<bool>,
 }

 /// Present if the server offers any prompt templates.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ServerCapabilitiesPrompts {
-    #[serde(rename = "listChanged")]
+    #[serde(
+        rename = "listChanged",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub list_changed: Option<bool>,
 }

@@ -948,6 +1151,7 @@ pub struct SubscribeRequestParams {
 /// Text provided to or from an LLM.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct TextContent {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<Annotations>,
    pub text: String,
    pub r#type: String, // &'static str = "text"
@@ -955,7 +1159,7 @@ pub struct TextContent {

 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct TextResourceContents {
-    #[serde(rename = "mimeType")]
+    #[serde(rename = "mimeType", default, skip_serializing_if = "Option::is_none")]
    pub mime_type: Option<String>,
    pub text: String,
    pub uri: String,
@@ -964,7 +1168,9 @@ pub struct TextResourceContents {
 /// Definition for a tool the client can call.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct Tool {
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub annotations: Option<ToolAnnotations>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub description: Option<String>,
    #[serde(rename = "inputSchema")]
    pub input_schema: ToolInputSchema,
@@ -974,7 +1180,9 @@ pub struct Tool {
 /// A JSON Schema object defining the expected parameters for the tool.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ToolInputSchema {
+    #[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"
 }
@@ -989,14 +1197,31 @@ pub struct ToolInputSchema {
 /// received from untrusted servers.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize)]
 pub struct ToolAnnotations {
-    #[serde(rename = "destructiveHint")]
+    #[serde(
+        rename = "destructiveHint",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub destructive_hint: Option<bool>,
-    #[serde(rename = "idempotentHint")]
+    #[serde(
+        rename = "idempotentHint",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub idempotent_hint: Option<bool>,
-    #[serde(rename = "openWorldHint")]
+    #[serde(
+        rename = "openWorldHint",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub open_world_hint: Option<bool>,
-    #[serde(rename = "readOnlyHint")]
+    #[serde(
+        rename = "readOnlyHint",
+        default,
+        skip_serializing_if = "Option::is_none"
+    )]
    pub read_only_hint: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub title: Option<String>,
 }