Fix KeyError: 'name' in qwen3_coder tool parser

[DShickle]

Fix KeyError: 'name' in qwen3_coder tool parser

Summary

qwen3_coder.py raises KeyError: 'name' when the tool list contains a function dict that doesn't have "name" at the top level of the "function" object. This causes the entire request to fail with a 500-level exception rather than gracefully skipping the malformed entry.

Root cause

In _get_arguments_config (line 29), the function dict is accessed with a hard bracket lookup:

if function["name"] == func_name:

Some clients (including Pi and other agentic coding tools) send tool definitions where the "function" object structure doesn't always include "name" — for example, MCP-proxied tool definitions or tools with non-standard shapes. When this happens, Python raises KeyError: 'name' and the server throws an unhandled exception.

Fix

Replace the hard lookup with .get():

if function.get("name") == func_name:

This is a one-line change. If "name" is absent, function.get("name") returns None, which won't match any func_name, so the loop simply continues to the next tool — the correct behaviour.

Traceback

File ".../mlx_lm/tool_parsers/qwen3_coder.py", line 115, in parse_tool_call
    return _parse_xml_function_call(match[0], tools)
File ".../mlx_lm/tool_parsers/qwen3_coder.py", line 85, in _parse_xml_function_call
    param_config = _get_arguments_config(function_name, tools)
File ".../mlx_lm/tool_parsers/qwen3_coder.py", line 29, in _get_arguments_config
    if function["name"] == func_name:
       ~~~~~~~~^^^^^^^^
KeyError: 'name'

Reproduction

1. Start mlx_lm.server with a Qwen3.6 or Qwen3-Coder model
2. Send a /v1/chat/completions request with tools via an agentic client (Pi, OpenCode, etc.)
3. The server crashes with KeyError: 'name' on the first tool call

Related

• Issue mlx_lm.server failed in qwen3.5 tools #905 (similar tool parser failure on Qwen3.5)

Testing

After applying the fix, tool calls from Pi (using MCP-proxied tool definitions) work correctly across multiple turns with no degradation.