Sanitize hostile ability input schemas before tool conversion

[dennisdornon]

What changed

convertInputSchema in src/tool-schema.ts now coerces a non-object properties field to {} and drops non-string entries from required before building the MCP tool definition. New src/tool-schema.test.ts pins the behavior with five regression tests (four failed before the fix).

Why

A PHP dashboard that registers an ability with an empty properties map serializes it as [], and the server passed that straight through to tools/list. Spec-compliant MCP clients validate the whole response, so one malformed ability took every tool offline: the official SDK rejects the payload with a zod error, and Claude Code showed the server as connected with zero usable tools. Two abilities on a dashboard experiment branch triggered this in practice.

This is the treat-remote-schemas-as-hostile rule applied to schema shape, not only to content.

Review focus

The coercion happens before the description backfill loop, so a malformed schema now yields a valid empty-input tool instead of poisoning the catalog. Check that you agree silently coercing (rather than dropping the ability) is the right failure mode; the ability is still callable and the dashboard-side schema bug stays visible in its own API output.

Verification

• npm test (446 passing, includes the 5 new regressions), npm run lint (0 errors), npm run format:check, npm run build
• Live: against the dashboard that served the malformed abilities, tools/list went from a client-side zod rejection to 71 valid tools, verified with the official MCP SDK client

https://claude.ai/code/session_01NnJiXybDffmpEsdwE1cnYT

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of malformed tool input schemas.
  • Invalid or non-object properties now default to an empty object.
  • Invalid required fields now default to an empty list, with non-string entries removed.

• Tests

  • Added coverage for malformed and valid input-schema scenarios.

[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

Run ID: e3740322-10fb-43ba-ad3d-fcd80b49129c

📥 Commits

Reviewing files that changed from the base of the PR and between a6d5efd and 261f973.

📒 Files selected for processing (2)

• src/tool-schema.test.ts
• src/tool-schema.ts

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Walkthrough

convertInputSchema now sanitizes malformed properties and required fields before producing MCP tools. New Vitest coverage verifies coercion, filtering, and preservation of valid input schemas.

Changes

Input Schema Sanitization

Layer / File(s)	Summary
Schema field sanitization src/tool-schema.ts	convertInputSchema coerces non-object or array properties to {} and non-array or mixed-type required values to an array of strings.
Schema normalization tests src/tool-schema.test.ts	Tests malformed properties and required values, filters non-string entries, and confirms valid schemas remain unchanged.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• mainwp/mainwp-mcp#28: Both changes modify MCP tool-schema generation and validation in src/tool-schema.ts.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: sanitizing hostile ability input schemas before converting them into tool definitions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 fix/sanitize-hostile-input-schemas

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 ESLint

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[dennisdornon]

Closing: this fix ships inside the upcoming code-review-cleanup PR, where it was developed alongside its acceptance-test coverage. Splitting it out was unnecessary.