fix(mcp): include threadId in both content and structuredContent in CallToolResult

codex-rs/docs/codex_mcp_interface.md

@@ -105,6 +105,25 @@ While a conversation runs, the server sends notifications:
 
 Clients should render events and, when present, surface approval requests (see next section).
 
+## Tool responses
+
+The `codex` and `codex-reply` tools return standard MCP `CallToolResult` payloads. For
+compatibility with MCP clients that prefer `structuredContent`, Codex mirrors the
+assistant text inside `structuredContent` alongside the `threadId`.
+
+Example:
+
+```json
+{
+  "content": [{ "type": "text", "text": "Hello from Codex" }],
+  "structuredContent": {
+    "threadId": "019bbed6-1e9e-7f31-984c-a05b65045719",
+    "text": "Hello from Codex",
+    "content": [{ "type": "text", "text": "Hello from Codex" }]
+  }
+}
+```
+
 ## Approvals (server → client)
 
 When Codex needs approval to apply changes or run commands, the server issues JSON‑RPC requests to the client:

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

@@ -34,21 +34,27 @@ pub(crate) const INVALID_PARAMS_ERROR_CODE: i64 = -32602;
 
 /// To adhere to MCP `tools/call` response format, include the Codex
 /// `threadId` in the `structured_content` field of the response.
-fn create_call_tool_result_with_thread_id(
+/// Some MCP clients ignore `content` when `structuredContent` is present, so
+/// mirror the text content there as well.
+pub(crate) fn create_call_tool_result_with_thread_id(
     thread_id: ThreadId,
     text: String,
     is_error: Option<bool>,
 ) -> CallToolResult {
+    let content = vec![ContentBlock::TextContent(TextContent {
+        r#type: "text".to_string(),
+        text: text.clone(),
+        annotations: None,
+    })];
+    let structured_content = json!({
+        "threadId": thread_id,
+        "text": text,
+        "content": content.clone(),
+    });
     CallToolResult {
-        content: vec![ContentBlock::TextContent(TextContent {
-            r#type: "text".to_string(),
-            text,
-            annotations: None,
-        })],
+        content,
         is_error,
-        structured_content: Some(json!({
-            "threadId": thread_id,
-        })),
+        structured_content: Some(structured_content),
     }
 }
 
@@ -398,6 +404,12 @@ mod tests {
             result.structured_content,
             Some(json!({
                 "threadId": thread_id,
+                "text": "done",
+                "content": vec![ContentBlock::TextContent(TextContent {
+                    r#type: "text".to_string(),
+                    text: "done".to_string(),
+                    annotations: None,
+                })],
             }))
         );
     }

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

@@ -498,17 +498,11 @@ impl MessageProcessor {
             Ok(c) => c,
             Err(_) => {
                 tracing::warn!("Session not found for thread_id: {thread_id}");
-                let result = CallToolResult {
-                    content: vec![ContentBlock::TextContent(TextContent {
-                        r#type: "text".to_owned(),
-                        text: format!("Session not found for thread_id: {thread_id}"),
-                        annotations: None,
-                    })],
-                    is_error: Some(true),
-                    structured_content: Some(json!({
-                        "threadId": thread_id,
-                    })),
-                };
+                let result = crate::codex_tool_runner::create_call_tool_result_with_thread_id(
+                    thread_id,
+                    format!("Session not found for thread_id: {thread_id}"),
+                    Some(true),
+                );
                 outgoing.send_response(request_id, result).await;
                 return;
             }

codex-rs/mcp-server/tests/suite/codex_tool.rs

@@ -162,6 +162,13 @@ async fn shell_command_approval_triggers_elicitation() -> anyhow::Result<()> {
                 ],
                 "structuredContent": {
                     "threadId": params.thread_id,
+                    "text": "File created!",
+                    "content": [
+                        {
+                            "text": "File created!",
+                            "type": "text"
+                        }
+                    ]
                 }
             }),
         },
@@ -323,6 +330,13 @@ async fn patch_approval_triggers_elicitation() -> anyhow::Result<()> {
                 ],
                 "structuredContent": {
                     "threadId": params.thread_id,
+                    "text": "Patch has been applied successfully!",
+                    "content": [
+                        {
+                            "text": "Patch has been applied successfully!",
+                            "type": "text"
+                        }
+                    ]
                 }
             }),
         },
@@ -394,6 +408,13 @@ async fn codex_tool_passes_base_instructions() -> anyhow::Result<()> {
                     .and_then(|v| v.get("threadId"))
                     .and_then(serde_json::Value::as_str)
                     .expect("codex tool response should include structuredContent.threadId"),
+                "text": "Enjoy!",
+                "content": [
+                    {
+                        "text": "Enjoy!",
+                        "type": "text"
+                    }
+                ]
             }
         })
     );