Consider always providing schema properties

[findleyr]

Following up on discussion in github/github-mcp-server#1548, this issue tracks deciding whether we want to always provide an empty "properties" field for schemas. For example could handle this in the jsonschema library for inferred schemas, and/or panic at tool registration time for user-defined schemas.

We should confirm whether "properties" is required by the JSON schema spec (after 5m search, I still don't know). If it is, then the answer is clear that we should enforce it. If not, we still may want to do so for compatibility purposes.

CC @jba

[findleyr]

More research indicates that {"type":"object"} is valid, and OpenAI is non-conforming.

With that said, it still may be a problem that we want to address. Elsewhere, we have a concept of 'strict' mode (unexported in the StreamableClientTransport). This may be another such case, and perhaps we should have a global SDK 'strict' boolean.

[SamMorrowDrums]

OpenAI is non-conforming

This was also our conclusion at GitHub, however we decided to support it for compatibility. SDK level has different priorities though.

Thanks for looking into it.

[findleyr]

Removing the bug tag since this isn't actually a bug.
We discussed this yesterday, and since GitHub has already worked around the issue for OpenAI, will probably not act on this issue until there is more evidence from other users. @SamMorrowDrums is there an OpenAI issue I can nudge? (no worries if not).

[SamMorrowDrums]

Thanks @findleyr I don't believe there's a specific issue.

Its certainly no problem for us, but I think a variety of people have ended up experiencing difficulties as a result. I'd be inclined to agree that if the spec doesn't require this, the SDK shouldn't. Hopefully the existence of this issue and the one on GH MCP will help people to self-solve.

• Support strict schemas for MCP tools openai/openai-agents-python#404
• OpenAI Agent Node Strict Tool Calling Mode fails on json schema validation with Custom MCP Tool FlowiseAI/Flowise#5109
• createAgent binds tools with strict:true for OpenAI langchain-ai/langchainjs#9496
• Tool failed in OpenAI structured-outputs strict mode langchain-ai/langmem#113
• Context7 MCP not working (Invalid schema for function 'context7_get-library-docs') sst/opencode#250
  exec bug - MCP Tool Conversion Error: firecrawl__firecrawl_extract openai/codex#4300
• MCP not support some open-source MCP servers openai/openai-agents-python#392
• jedarden/CLASP@e9afc65

https://community.openai.com/t/schema-additionalproperties-must-be-false-when-strict-is-true/929996