diff --git a/codex-rs/mcp-types/generate_mcp_types.py b/codex-rs/mcp-types/generate_mcp_types.py
index 6066423f55..c597836be6 100755
--- a/codex-rs/mcp-types/generate_mcp_types.py
+++ b/codex-rs/mcp-types/generate_mcp_types.py
@@ -50,7 +50,7 @@ def main() -> int:
     DEFINITIONS = schema_json["definitions"]
 
     out = [
-        """
+        f"""
 // @generated
 // DO NOT EDIT THIS FILE DIRECTLY.
 // Run the following in the crate root to regenerate this file:
@@ -67,17 +67,19 @@ pub const MCP_SCHEMA_VERSION: &str = "{SCHEMA_VERSION}";
 pub const JSONRPC_VERSION: &str = "{JSONRPC_VERSION}";
 
 /// Paired request/response types for the Model Context Protocol (MCP).
-pub trait ModelContextProtocolRequest {
+pub trait ModelContextProtocolRequest {{
     const METHOD: &'static str;
     type Params: DeserializeOwned + Serialize + Send + Sync + 'static;
     type Result: DeserializeOwned + Serialize + Send + Sync + 'static;
-}
+}}
 
 /// One-way message in the Model Context Protocol (MCP).
-pub trait ModelContextProtocolNotification {
+pub trait ModelContextProtocolNotification {{
     const METHOD: &'static str;
     type Params: DeserializeOwned + Serialize + Send + Sync + 'static;
-}
+}}
+
+fn default_jsonrpc() -> String {{ JSONRPC_VERSION.to_owned() }}
 
 fn default_jsonrpc() -> String {{ JSONRPC_VERSION.to_owned() }}