fix: ensure output of codex-rs/mcp-types/generate_mcp_types.py matches codex-rs/mcp-types/src/lib.rs

codex-rs/core/src/mcp_connection_manager.rs

@@ -17,7 +17,7 @@ use anyhow::Result;
 use anyhow::anyhow;
 use codex_mcp_client::McpClient;
 use mcp_types::ClientCapabilities;
-use mcp_types::McpClientInfo;
+use mcp_types::Implementation;
 use mcp_types::Tool;
 
 use serde_json::json;
@@ -159,10 +159,14 @@ impl McpConnectionManager {
                                 // indicates this should be an empty object.
                                 elicitation: Some(json!({})),
                             },
-                            client_info: McpClientInfo {
+                            client_info: Implementation {
                                 name: "codex-mcp-client".to_owned(),
                                 version: env!("CARGO_PKG_VERSION").to_owned(),
                                 title: Some("Codex".into()),
+                                // This field is used by Codex when it is an MCP
+                                // server: it should not be used when Codex is
+                                // an MCP client.
+                                user_agent: None,
                             },
                             protocol_version: mcp_types::MCP_SCHEMA_VERSION.to_owned(),
                         };

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

@@ -17,10 +17,10 @@ use anyhow::Context;
 use anyhow::Result;
 use codex_mcp_client::McpClient;
 use mcp_types::ClientCapabilities;
+use mcp_types::Implementation;
 use mcp_types::InitializeRequestParams;
 use mcp_types::ListToolsRequestParams;
 use mcp_types::MCP_SCHEMA_VERSION;
-use mcp_types::McpClientInfo;
 use tracing_subscriber::EnvFilter;
 
 #[tokio::main]
@@ -60,10 +60,13 @@ async fn main() -> Result<()> {
             sampling: None,
             elicitation: None,
         },
-        client_info: McpClientInfo {
+        client_info: Implementation {
             name: "codex-mcp-client".to_owned(),
             version: env!("CARGO_PKG_VERSION").to_owned(),
             title: Some("Codex".to_string()),
+            // This field is used by Codex when it is an MCP server: it should
+            // not be used when Codex is an MCP client.
+            user_agent: None,
         },
         protocol_version: MCP_SCHEMA_VERSION.to_owned(),
     };

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

@@ -234,7 +234,7 @@ impl MessageProcessor {
             },
             instructions: None,
             protocol_version: params.protocol_version.clone(),
-            server_info: mcp_types::McpServerInfo {
+            server_info: mcp_types::Implementation {
                 name: "codex-mcp-server".to_string(),
                 version: env!("CARGO_PKG_VERSION").to_string(),
                 title: Some("Codex".to_string()),

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

@@ -26,13 +26,13 @@ use codex_protocol::mcp_protocol::SendUserTurnParams;
 
 use mcp_types::CallToolRequestParams;
 use mcp_types::ClientCapabilities;
+use mcp_types::Implementation;
 use mcp_types::InitializeRequestParams;
 use mcp_types::JSONRPC_VERSION;
 use mcp_types::JSONRPCMessage;
 use mcp_types::JSONRPCNotification;
 use mcp_types::JSONRPCRequest;
 use mcp_types::JSONRPCResponse;
-use mcp_types::McpClientInfo;
 use mcp_types::ModelContextProtocolNotification;
 use mcp_types::ModelContextProtocolRequest;
 use mcp_types::RequestId;
@@ -134,10 +134,11 @@ impl McpProcess {
                 roots: None,
                 sampling: None,
             },
-            client_info: McpClientInfo {
+            client_info: Implementation {
                 name: "elicitation test".into(),
                 title: Some("Elicitation Test".into()),
                 version: "0.0.0".into(),
+                user_agent: None,
             },
             protocol_version: mcp_types::MCP_SCHEMA_VERSION.into(),
         };

codex-rs/mcp-types/generate_mcp_types.py

@@ -265,8 +265,11 @@ class StructField:
     name: str
     type_name: str
     serde: str | None = None
+    comment: str | None = None
 
     def append(self, out: list[str], supports_const: bool) -> None:
+        if self.comment:
+            out.append(f"    // {self.comment}\n")
         if self.serde:
             out.append(f"    {self.serde}\n")
         if self.viz == "const":
@@ -312,6 +315,18 @@ def define_struct(
         else:
             fields.append(StructField("pub", rs_prop.name, prop_type, rs_prop.serde))
 
+    # Special-case: add Codex-specific user_agent to Implementation
+    if name == "Implementation":
+        fields.append(
+            StructField(
+                "pub",
+                "user_agent",
+                "Option<String>",
+                '#[serde(default, skip_serializing_if = "Option::is_none")]',
+                "This is an extra field that the Codex MCP server sends as part of InitializeResult.",
+            )
+        )
+
     if implements_request_trait(name):
         add_trait_impl(name, "ModelContextProtocolRequest", fields, out)
     elif implements_notification_trait(name):

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

@@ -482,20 +482,12 @@ pub struct ImageContent {
 
 /// Describes the name and version of an MCP implementation, with an optional title for UI representation.
 #[derive(Debug, Clone, PartialEq, Deserialize, Serialize, TS)]
-pub struct McpClientInfo {
-    pub name: String,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub title: Option<String>,
-    pub version: String,
-}
-
-/// Describes the name and version of an MCP implementation, with an optional title for UI representation.
-#[derive(Debug, Clone, PartialEq, Deserialize, Serialize, TS)]
-pub struct McpServerInfo {
+pub struct Implementation {
     pub name: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub title: Option<String>,
     pub version: String,
+    // This is an extra field that the Codex MCP server sends as part of InitializeResult.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub user_agent: Option<String>,
 }
@@ -513,7 +505,7 @@ impl ModelContextProtocolRequest for InitializeRequest {
 pub struct InitializeRequestParams {
     pub capabilities: ClientCapabilities,
     #[serde(rename = "clientInfo")]
-    pub client_info: McpClientInfo,
+    pub client_info: Implementation,
     #[serde(rename = "protocolVersion")]
     pub protocol_version: String,
 }
@@ -527,7 +519,7 @@ pub struct InitializeResult {
     #[serde(rename = "protocolVersion")]
     pub protocol_version: String,
     #[serde(rename = "serverInfo")]
-    pub server_info: McpServerInfo,
+    pub server_info: Implementation,
 }
 
 impl From<InitializeResult> for serde_json::Value {

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

@@ -1,10 +1,10 @@
 use mcp_types::ClientCapabilities;
 use mcp_types::ClientRequest;
+use mcp_types::Implementation;
 use mcp_types::InitializeRequestParams;
 use mcp_types::JSONRPC_VERSION;
 use mcp_types::JSONRPCMessage;
 use mcp_types::JSONRPCRequest;
-use mcp_types::McpClientInfo;
 use mcp_types::RequestId;
 use serde_json::json;
 
@@ -58,10 +58,11 @@ fn deserialize_initialize_request() {
                 sampling: None,
                 elicitation: None,
             },
-            client_info: McpClientInfo {
+            client_info: Implementation {
                 name: "acme-client".into(),
                 title: Some("Acme".to_string()),
                 version: "1.2.3".into(),
+                user_agent: None,
             },
             protocol_version: "2025-06-18".into(),
         }