Provider API rejects tool_search function calls from Codex clients with 400 "Missing required parameter: 'input[N].arguments'"

[Lv-Guu]

Summary

When using Codex (OpenAI's CLI/desktop agent) through the Command Code Provider API (/provider/v1/chat/completions), any request where the assistant calls the tool_search function fails with HTTP 400. This is Codex's standard tool-discovery mechanism — every new tool (web search, MCP tools, plugin tools) requires a tool_search call first. As a result, Codex cannot use web search, MCP servers, or plugin tools at all through Command Code.

Note: this is about the Provider API gateway, not the Command Code CLI (cmd).

Expected Behavior

tool_search should be accepted as a normal function call (like any other function in tool_calls), same as OpenAI's official API and other OpenAI-compatible gateways do. Codex relies on it to discover and load tools.

Actual Behavior

HTTP 400 with an empty-ish error body. When routed through a proxy (e.g. cc-switch), the error surfaces as:
"Missing required parameter: 'input[N].arguments'"

Verified with direct API calls:

• tool_search listed in the tools array (definition only): 200 OK
• assistant calls tool_search in tool_calls: 400
• same request shape with a different function name (e.g. get_weather): 200 OK
  This confirms the gateway specifically rejects invoking a function named tool_search.

Steps to reproduce the issue

1. POST https://api.commandcode.ai/provider/v1/chat/completions with Authorization: Bearer
2. Body:
   {
   "model": "gpt-5.6-sol",
   "messages": [
   {"role": "user", "content": "hi"},
   {"role": "assistant", "content": null, "tool_calls": [
   {"id": "call_1", "type": "function", "function": {"name": "tool_search", "arguments": "{"limit":5,"query":"demo"}"}}
   ]}
   ],
   "tools": [
   {"type": "function", "function": {"name": "tool_search", "description": "Search for tools", "parameters": {"type": "object", "properties": {"query": {"type": "string"}, "limit": {"type": "integer"}}, "required": ["query"]}}}
   ]
   }
3. Observe HTTP 400
4. Replace "tool_search" with "get_weather" in both places → 200 OK

Command Code Version

Provider API (gateway) — subscription: GOAT plan

Operating System

Windows

Terminal/IDE

Codex desktop / Codex CLI

Shell

powershell

Session file (optional)

No response

Fix prompt (optional)

No response

Additional context

This same class of problem (strict gateways rejecting Codex's tool_search / namespace tool types) is documented in other projects:

• Responses API: ResponseToolUnion rejects "namespace" and "tool_search" tool types emitted by OpenAI Codex CLI envoyproxy/ai-gateway#2164: "ResponseToolUnion rejects namespace and tool_search tool types emitted by OpenAI Codex CLI"
• [P0 / Blocker] Remote compact task fails 100% with "tools.defer_loading requires tools.tool_search" — GPT-5.5 unusable at context limit, no client-side workaround openai/codex#19486: "tools.defer_loading requires tools.tool_search"
• diegosouzapw/OmniRoute PR #7571: "stop dropping tool_search in Responses->Chat translation"

The official OpenAI API accepts these calls; Command Code's gateway appears to have a gap in its Chat Completions implementation. Please either accept tool_search invocations or document the limitation.