Document the MCP trace viewer in Codex

[petyosi]

Summary

• document how to ask Codex to display a known Logfire trace
• describe the inline span tree, waterfall, lazy details, and Logfire handoff
• state the initial Codex-only inline-rendering boundary and fallback behavior for other MCP clients
• add trace_get and trace_span_get to the MCP tool-family table

Companion implementation: https://github.com/pydantic/platform/pull/27163

Verification

• uv run pre-commit run --files docs/how-to-guides/mcp-server.md

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 6b3e4e46-c2d3-40f3-b1eb-3a04b322e2b1

📥 Commits

Reviewing files that changed from the base of the PR and between 65d5688 and a987d5d.

📒 Files selected for processing (1)

• docs/how-to-guides/mcp-server.md

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• pydantic/logfire (manual)
• pydantic/pydantic-ai (manual)
• pydantic/pydantic (auto-detected)

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📝 Walkthrough

Walkthrough

Updated the MCP server guide with instructions for inspecting a known trace ID in Codex through Logfire, including the inline trace viewer behavior. Added trace_get and trace_span_get to the available MCP tools table under the Traces tool family.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	It clearly summarizes the main change: documenting Codex's MCP trace viewer.
Description check	✅ Passed	It describes the documented Codex trace viewer behavior and MCP tool additions.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch docs/mcp-trace-viewer

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[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

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