fix: flatten top-level anyOf/oneOf/allOf in MCP tool schemas

[daniel-lxs]

Problem

MCP servers can define tool schemas with anyOf, oneOf, or allOf at the top level. When these schemas are passed to OpenRouter with Anthropic models, the API rejects them with:

ApiProviderError: tools.19.custom.input_schema: input_schema does not support oneOf, allOf, or anyOf at the top level

PostHog Issue: https://us.posthog.com/error_tracking/019bb5ab-be91-7160-8060-06f185ee5fcb

Solution

Extended normalizeToolSchema() in src/utils/json-schema.ts to flatten top-level schema composition keywords before sending to providers.

Changes:

1. Added flattenTopLevelComposition() function that:

   • Detects schemas with anyOf, oneOf, or allOf at the top level
   • Extracts the first object-type variant from the composition
   • Merges it with any top-level metadata (like description, $schema)
   • Falls back to a generic { type: "object", additionalProperties: false } if no object variant exists

2. Updated tests in src/utils/__tests__/json-schema.spec.ts

Impact

The model sees a slightly simplified schema (just the object type, not "object OR null"). In practice, most MCP tools expect object inputs anyway, so the model's generated calls remain valid. The MCP server performs its own validation regardless of what schema we send to the LLM.

Testing

All 5242 tests pass.

Closes COM-485

---

Important

Flatten top-level anyOf, oneOf, allOf in MCP tool schemas for provider compatibility in normalizeToolSchema().

• Behavior:
  • normalizeToolSchema() in json-schema.ts now flattens top-level anyOf, oneOf, allOf to a single object schema using flattenTopLevelComposition().
  • Falls back to { type: "object", additionalProperties: false } if no object variant exists.
• Tests:
  • Added tests in json-schema.spec.ts to verify flattening of top-level schema composition keywords.
  • Ensures nested anyOf remains unchanged.
• Misc:
  • Updated comments and documentation in json-schema.ts to reflect new functionality.

^{This description was created by for 6476e00. You can customize this summary. It will automatically update as commits are pushed.}

[roomote]

Rooviewer   See task on Roo Cloud

Review complete. No issues found.

The implementation correctly flattens top-level anyOf/oneOf/allOf schemas for OpenRouter/Claude provider compatibility. The code is well-tested with comprehensive coverage of edge cases.

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}