# Todo 27: EventAgent Tool Arguments

## Status

done

## Goal

Stop EventAgent turns from ending with `event agent did not return arguments for mock_search` when the compatible provider fails to return a tool call in the exact shape the parser expects.

## Root Cause

EventAgent currently sends one tool schema to the LLM and expects the stream parser to emit a provider tool-call event. There are two brittle points:

- The OpenAI-compatible request includes `tools` but does not force the single tool through `tool_choice`.
- The stream parser only drains accumulated provider tool calls when `finish_reason == "tool_calls"`, so providers that end with another terminal reason can drop the accumulated tool call.

If neither path emits an event, EventAgent raises a ValueError and the tool result becomes a handler error.

## Scope

- Force the single supplied tool in OpenAI-compatible requests.
- Drain accumulated provider tool calls on any terminal finish reason.
- Add an EventAgent fallback to registry/context argument resolution when the LLM returns no tool call.
- Keep ChatAgent tool-free.

## Verification

- Failing parser test for terminal `finish_reason="stop"` with accumulated tool call.
- Failing OpenAI client payload test for `tool_choice`.
- Failing EventAgent test for no-tool-call fallback.
- `uv run pytest tests/test_openai_stream_parser.py tests/test_event_agent.py tests/test_websocket_api.py::test_openai_chat_client_streams_sse_chunks_through_parser -q` passes: 9 tests.
- `uv run pytest` passes: 53 tests.