fix(mcp): reject conflicting exclusions on shared operations - #115566

Problem

• An MCP tool author can silently ship the wrong request schema when two enabled tools share one API operation and list different exclude_params.
• Codegen builds one schema per operation, so one tool's exclusions quietly apply to the other.

Supersedes #111366 (closed), rebased on current master. Fork handoff: Silthus/posthog#344.

Changes

• MCP codegen now fails when enabled tools on a shared operation list different exclusions within one YAML file. The error names the operation and asks for matching exclude_params.
• A missing list counts as empty. Order and duplicates do not matter, and disabled tools do not count.
• Rejected alternative: per-tool exclusions on a shared operation. No tool needs them yet.
• Mechanical: a note in implementing-mcp-tools.md.

How did you test this code?

Test rationale: the existing generate-tools tests generate one tool at a time, so they cannot see two tools overwrite each other. The new tool-definitions.test.ts cases fail on the old parser.

• Ran services/mcp/tests/unit/tool-definitions.test.ts locally on the rebased branch: it passes.
• Not run locally: full hogli build:openapi. The reviewer ran the check over all 69 tool YAML files on master, and none conflict.

Release status

• No feature flag controls this change

Docs update

Updated docs/published/handbook/engineering/ai/implementing-mcp-tools.md with the new rule.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Agent: T3 Code with Claude Code, Claude Opus 5.5 (claude-opus-5-5). Cross-family review: Codex, GPT-6.1 Sol (gpt-6.1-sol), high reasoning effort, read-only.

• Rebuilt from the closed PR's diff on master 60187c17de7. The patch applied without changes.
• Skills: writing-pr-descriptions, writing-tests, merge-risk.
• Review: no findings.
• Duplicate search found no open PR for this check. fix(mcp): fail codegen when a yaml setting names no field #112861 extends the no-field check to other settings, which is a different rule.