fix: MCP tool compatibility with OpenAI strict mode #255
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OpenAI defaults to strict=true for tools, which: 1. Rejects JSON Schema `format` fields (e.g., "format": "uri") 2. Requires all properties to be in the `required` array MCP tools use standard JSON Schema conventions where optional parameters (with defaults) are NOT in `required`. Setting strict=false bypasses OpenAI's strict mode validation, allowing MCP tool schemas to work as-is. Changes: - Add `strict` parameter to Tool class constructor - Set strict=false for MCP tools in Tool.from_mcp() - Make rm_param_titles() properly recursive with isinstance check - Update VCR cassettes for MCP client tests Note: This does NOT strip the `format` field from schemas because strict=false makes OpenAI accept it. This is a simpler fix that avoids unnecessary schema mutation. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <[email protected]>
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Summary
Fixes MCP tools (like
mcp-server-fetch) failing with OpenAI providers due to strict mode schema validation.Problem
OpenAI defaults to
strict=truefor function tools, which enforces:formatfields (e.g.,"format": "uri"is rejected)requiredarrayMCP tools use standard JSON Schema conventions where optional parameters with defaults are NOT in
required. This caused errors like:Solution
Set
strict=falsefor MCP tools, which bypasses OpenAI's strict mode validation and allows standard JSON Schema conventions.This is the minimal fix - we intentionally don't strip
formatfields from schemas becausestrict=falsemakes OpenAI accept them as-is.Changes
strictparameter toToolclass constructorstrict=falsefor MCP tools inTool.from_mcp()rm_param_titles()properly recursive (fixes latent bug with nested schemas)Testing
ChatOpenAI,ChatOpenAICompletions, andChatAnthropicmcp-server-fetchRelated