fix: add additionalProperties: false to nested MCP tool schemas #10109
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Review complete. No issues found. The latest changes pin zod to version 3.25.61 to avoid a TypeScript TS2589 regression introduced in 3.25.76. This is a clean, targeted fix that correctly pins the dependency version and updates the lockfile accordingly. Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues. |
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Dec 16, 2025
OpenAI's API requires additionalProperties: false on all object schemas, including nested ones. MCP tools like 'create_entities' have array items that are objects, which were missing this property. Created a recursive utility function that transforms JSON schemas to ensure all nested object schemas have additionalProperties: false.
- Add JsonSchema TypeScript interface for type safety - Add JsonSchemaSchema Zod validator for validating JSON Schema structures - Add JsonSchemaUtils class with validation methods: - validate(): safe validation with result object - validateOrThrow(): throws on invalid schema - isValid(): type guard for checking validity - stripUnknownFields(): sanitize schemas - validateAndAddAdditionalPropertiesFalse(): combined validation + transform - Keep standalone addAdditionalPropertiesFalse() for backwards compatibility - Expand test coverage from 12 to 29 tests
- Replace custom recursive traversal with json-schema-traverse library - Library is small (~22KB), has TypeScript types, and is well-tested - Same author as ajv (most popular JSON Schema validator) - Simplifies the addAdditionalPropertiesFalse implementation - All 29 tests still pass
- Keep Zod validation for JSON Schema structure - Add generic transformJsonSchema() function for extensibility - Remove unused JsonSchemaUtils class - Reduce code while maintaining all functionality
- Single schema definition (StrictJsonSchemaSchema) that validates AND applies defaults - Removed json-schema-traverse dependency - mcp_server.ts uses parsed schema directly, no manual property additions - Updated tests to verify Zod default behavior
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Problem
OpenAI's API returns an error when MCP tools have nested object schemas that don't have
additionalProperties: false:Solution
Uses Zod schema with
.default(false)onadditionalProperties. A single schema definition that is both validator AND mutator - no manual property additions needed.API
JsonSchemaSchemaStrictJsonSchemaSchemaadditionalProperties: falseto all schemas via Zod's.default()Usage
Changes
src/utils/json-schema.ts- Single Zod schema with.default(false)onadditionalPropertiessrc/core/prompts/tools/native-tools/mcp_server.ts- Uses parsed schema directlyjson-schema-traversedependencyTesting
All 4700+ tests pass.
Important
Adds
ToolInputSchemato ensureadditionalProperties: falsein nested schemas, updatesgetMcpServerTools(), and adds tests.additionalProperties: falsein nested schemas usingToolInputSchemainjson-schema.ts.getMcpServerTools()inmcp_server.tsto useToolInputSchemafor schema parsing.json-schema.spec.tsto verifyToolInputSchemabehavior.json-schema-traversedependency.zodversion inpackage.json.This description was created by
for a93c1a7. You can customize this summary. It will automatically update as commits are pushed.