diff --git a/codex-rs/core/src/tools/context.rs b/codex-rs/core/src/tools/context.rs
index 43d25aa1f5..9bd8440399 100644
--- a/codex-rs/core/src/tools/context.rs
+++ b/codex-rs/core/src/tools/context.rs
@@ -38,7 +38,6 @@ pub enum ToolPayload {
     Mcp {
         server: String,
         tool: String,
-        arguments: Option<serde_json::Value>,
         raw_arguments: String,
     },
 }
diff --git a/codex-rs/core/src/tools/handlers/mcp.rs b/codex-rs/core/src/tools/handlers/mcp.rs
index 7c533fbbd7..17eae7ea7c 100644
--- a/codex-rs/core/src/tools/handlers/mcp.rs
+++ b/codex-rs/core/src/tools/handlers/mcp.rs
@@ -32,9 +32,8 @@ impl ToolHandler for McpHandler {
             ToolPayload::Mcp {
                 server,
                 tool,
-                arguments,
                 raw_arguments,
-            } => (server, tool, arguments, raw_arguments),
+            } => (server, tool, raw_arguments),
             _ => {
                 return Err(FunctionCallError::RespondToModel(
                     "mcp handler received unsupported payload".to_string(),
@@ -42,7 +41,7 @@ impl ToolHandler for McpHandler {
             }
         };
 
-        let (server, tool, _arguments, raw_arguments) = payload;
+        let (server, tool, raw_arguments) = payload;
         let arguments_str = raw_arguments;
 
         let response = handle_mcp_tool_call(
diff --git a/codex-rs/core/src/tools/router.rs b/codex-rs/core/src/tools/router.rs
index 56d04fd62c..8ec02ccd71 100644
--- a/codex-rs/core/src/tools/router.rs
+++ b/codex-rs/core/src/tools/router.rs
@@ -53,22 +53,12 @@ impl Router {
                 ..
             } => {
                 if let Some((server, tool)) = session.parse_mcp_tool_name(&name) {
-                    let parsed_arguments = if arguments.trim().is_empty() {
-                        None
-                    } else {
-                        Some(serde_json::from_str(&arguments).map_err(|err| {
-                            FunctionCallError::RespondToModel(format!(
-                                "failed to parse tool call arguments: {err}"
-                            ))
-                        })?)
-                    };
                     Ok(Some(ToolCall {
                         tool_name: name,
                         call_id,
                         payload: ToolPayload::Mcp {
                             server,
                             tool,
-                            arguments: parsed_arguments,
                             raw_arguments: arguments,
                         },
                     }))