Prompt: Tool Execution Metrics (2025-10-17)

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Required Reading

  • docs/20251017/tool-metrics.md
  • docs/design/tools-mcp.md
  • lib/codex/tools.ex, lib/codex/tools/registry.ex
  • test/codex/tools_test.exs, test/codex/thread_auto_run_test.exs

TDD Checklist

  1. Red – author tests for metrics and telemetry:
    • Unit tests verifying Codex.Tools.metrics/0 counters update on success/failure.
    • Test for reset_metrics/0 clearing state.
    • Integration test covering retry path in auto-run updating failure then success counts.
    • Telemetry assertion capturing [:codex, :tool, ...] events.
  2. Green – implement ETS-backed metrics, wrap invocations with timing, emit telemetry.
  3. Refactor – ensure concurrency safety, document API, run mix format, mix test, mix codex.verify.