fix: align task response types with MCP spec (#658)

crates/rmcp/src/handler/server.rs

@@ -116,15 +116,15 @@ impl<H: ServerHandler> Service<RoleServer> for H {
             ClientRequest::GetTaskInfoRequest(request) => self
                 .get_task_info(request.params, context)
                 .await
-                .map(ServerResult::GetTaskInfoResult),
+                .map(ServerResult::GetTaskResult),
             ClientRequest::GetTaskResultRequest(request) => self
                 .get_task_result(request.params, context)
                 .await
-                .map(ServerResult::TaskResult),
+                .map(ServerResult::GetTaskPayloadResult),
             ClientRequest::CancelTaskRequest(request) => self
                 .cancel_task(request.params, context)
                 .await
-                .map(ServerResult::empty),
+                .map(ServerResult::CancelTaskResult),
         }
     }
 
@@ -339,7 +339,8 @@ pub trait ServerHandler: Sized + Send + Sync + 'static {
         &self,
         request: GetTaskInfoParams,
         context: RequestContext<RoleServer>,
-    ) -> impl Future<Output = Result<GetTaskInfoResult, McpError>> + Send + '_ {
+    ) -> impl Future<Output = Result<GetTaskResult, McpError>> + Send + '_ {
+        let _ = (request, context);
         std::future::ready(Err(McpError::method_not_found::<GetTaskInfoMethod>()))
     }
 
@@ -347,7 +348,7 @@ pub trait ServerHandler: Sized + Send + Sync + 'static {
         &self,
         request: GetTaskResultParams,
         context: RequestContext<RoleServer>,
-    ) -> impl Future<Output = Result<TaskResult, McpError>> + Send + '_ {
+    ) -> impl Future<Output = Result<GetTaskPayloadResult, McpError>> + Send + '_ {
         let _ = (request, context);
         std::future::ready(Err(McpError::method_not_found::<GetTaskResultMethod>()))
     }
@@ -356,7 +357,7 @@ pub trait ServerHandler: Sized + Send + Sync + 'static {
         &self,
         request: CancelTaskParams,
         context: RequestContext<RoleServer>,
-    ) -> impl Future<Output = Result<(), McpError>> + Send + '_ {
+    ) -> impl Future<Output = Result<CancelTaskResult, McpError>> + Send + '_ {
         let _ = (request, context);
         std::future::ready(Err(McpError::method_not_found::<CancelTaskMethod>()))
     }
@@ -543,7 +544,7 @@ macro_rules! impl_server_handler_for_wrapper {
                 &self,
                 request: GetTaskInfoParams,
                 context: RequestContext<RoleServer>,
-            ) -> impl Future<Output = Result<GetTaskInfoResult, McpError>> + Send + '_ {
+            ) -> impl Future<Output = Result<GetTaskResult, McpError>> + Send + '_ {
                 (**self).get_task_info(request, context)
             }
 
@@ -551,7 +552,7 @@ macro_rules! impl_server_handler_for_wrapper {
                 &self,
                 request: GetTaskResultParams,
                 context: RequestContext<RoleServer>,
-            ) -> impl Future<Output = Result<TaskResult, McpError>> + Send + '_ {
+            ) -> impl Future<Output = Result<GetTaskPayloadResult, McpError>> + Send + '_ {
                 (**self).get_task_result(request, context)
             }
 
@@ -559,7 +560,7 @@ macro_rules! impl_server_handler_for_wrapper {
                 &self,
                 request: CancelTaskParams,
                 context: RequestContext<RoleServer>,
-            ) -> impl Future<Output = Result<(), McpError>> + Send + '_ {
+            ) -> impl Future<Output = Result<CancelTaskResult, McpError>> + Send + '_ {
                 (**self).cancel_task(request, context)
             }
         }

crates/rmcp/src/model.rs

@@ -2537,14 +2537,9 @@ impl RequestParamsMeta for CancelTaskParams {
 /// Deprecated: Use [`CancelTaskParams`] instead (SEP-1319 compliance).
 #[deprecated(since = "0.13.0", note = "Use CancelTaskParams instead")]
 pub type CancelTaskParam = CancelTaskParams;
-#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
-#[serde(rename_all = "camelCase")]
-#[serde(deny_unknown_fields)]
-#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
-pub struct GetTaskInfoResult {
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub task: Option<crate::model::Task>,
-}
+/// Deprecated: Use [`GetTaskResult`] instead (spec alignment).
+#[deprecated(since = "0.15.0", note = "Use GetTaskResult instead")]
+pub type GetTaskInfoResult = GetTaskResult;
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Default)]
 #[serde(rename_all = "camelCase")]
@@ -2720,9 +2715,10 @@ ts_union!(
     | EmptyResult
     | CreateTaskResult
     | ListTasksResult
-    | GetTaskInfoResult
-    | TaskResult
+    | GetTaskResult
+    | CancelTaskResult
     | CustomResult
+    | GetTaskPayloadResult
     ;
 );
 

crates/rmcp/src/model/task.rs

@@ -1,6 +1,8 @@
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
+use super::Meta;
+
 /// Canonical task lifecycle status as defined by SEP-1686.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
 #[serde(rename_all = "snake_case")]
@@ -19,21 +21,10 @@ pub enum TaskStatus {
     Cancelled,
 }
 
-/// Final result for a succeeded task (returned from `tasks/result`).
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
-#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
-pub struct TaskResult {
-    /// MIME type or custom content-type identifier.
-    pub content_type: String,
-    /// The actual result payload, matching the underlying request's schema.
-    pub value: Value,
-    /// Optional short summary for UI surfaces.
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub summary: Option<String>,
-}
-
 /// Primary Task object that surfaces metadata during the task lifecycle.
+///
+/// Per spec, `lastUpdatedAt` and `ttl` are required fields.
+/// `ttl` is nullable (`null` means unlimited retention).
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
 #[serde(rename_all = "camelCase")]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
@@ -48,10 +39,9 @@ pub struct Task {
     /// ISO-8601 creation timestamp.
     pub created_at: String,
     /// ISO-8601 timestamp for the most recent status change.
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub last_updated_at: Option<String>,
+    pub last_updated_at: String,
     /// Retention window in milliseconds that the receiver agreed to honor.
-    #[serde(skip_serializing_if = "Option::is_none")]
+    /// `None` (serialized as `null`) means unlimited retention.
     pub ttl: Option<u64>,
     /// Suggested polling interval (milliseconds).
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -66,6 +56,43 @@ pub struct CreateTaskResult {
     pub task: Task,
 }
 
+/// Response to a `tasks/get` request.
+///
+/// Per spec, `GetTaskResult = allOf[Result, Task]` — the Task fields are
+/// flattened at the top level, not nested under a `task` key.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct GetTaskResult {
+    #[serde(rename = "_meta", default, skip_serializing_if = "Option::is_none")]
+    pub meta: Option<Meta>,
+    #[serde(flatten)]
+    pub task: Task,
+}
+
+/// Response to a `tasks/result` request.
+///
+/// Per spec, the result structure matches the original request type
+/// (e.g., `CallToolResult` for `tools/call`). This is represented as
+/// an open object. The payload is the original request's result
+/// serialized as a JSON value.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct GetTaskPayloadResult(pub Value);
+
+/// Response to a `tasks/cancel` request.
+///
+/// Per spec, `CancelTaskResult = allOf[Result, Task]` — same shape as `GetTaskResult`.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub struct CancelTaskResult {
+    #[serde(rename = "_meta", default, skip_serializing_if = "Option::is_none")]
+    pub meta: Option<Meta>,
+    #[serde(flatten)]
+    pub task: Task,
+}
+
 /// Paginated list of tasks
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]