From 25a9949c49194d5a64de54a11bcc5b4724ac9bd5 Mon Sep 17 00:00:00 2001
From: Michael Bolin <mbolin@openai.com>
Date: Wed, 28 May 2025 17:17:21 -0700
Subject: [PATCH] fix: ensure inputSchema for MCP tool always has "properties"
 field when talking to OpenAI (#1150)

As noted in the comment introduced in this PR, this is analogous to the
issue reported in
https://github.com/openai/openai-agents-python/issues/449. This seems to
work now.
---
 codex-rs/core/src/client.rs | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/codex-rs/core/src/client.rs b/codex-rs/core/src/client.rs
index 57534e2f..72ce845f 100644
--- a/codex-rs/core/src/client.rs
+++ b/codex-rs/core/src/client.rs
@@ -280,12 +280,26 @@ fn mcp_tool_to_openai_tool(
     fully_qualified_name: String,
     tool: mcp_types::Tool,
 ) -> serde_json::Value {
+    let mcp_types::Tool {
+        description,
+        mut input_schema,
+        ..
+    } = tool;
+
+    // OpenAI models mandate the "properties" field in the schema. The Agents
+    // SDK fixed this by inserting an empty object for "properties" if it is not
+    // already present https://github.com/openai/openai-agents-python/issues/449
+    // so here we do the same.
+    if input_schema.properties.is_none() {
+        input_schema.properties = Some(serde_json::Value::Object(serde_json::Map::new()));
+    }
+
     // TODO(mbolin): Change the contract of this function to return
     // ResponsesApiTool.
     json!({
         "name": fully_qualified_name,
-        "description": tool.description,
-        "parameters": tool.input_schema,
+        "description": description,
+        "parameters": input_schema,
         "type": "function",
     })
 }