The tuple/list branch put the win32com VARIANT built for SetVariable into the
returned dict. The system_set_variable tool returns that dict verbatim under
output_schema {"type": "object"}; pydantic cannot serialise a VARIANT, FastMCP
drops the structured content and the client sees "outputSchema defined but no
structured output returned" -- after AutoCAD had already applied the write, so
every raw point-variable write (LIMMIN, LIMMAX, GRIDUNIT, SNAPUNIT, INSBASE)
was a retry/undo trap on the live engine while the audit log said TOOL OK.
The VARIANT is now only the SetVariable argument; "value" carries the
coerced Python list. The fake-ActiveX test asserts the reply, and a new
Client(server.mcp) test drives the tool through the output schema so the
serialisation path is covered.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd
