Add _meta Field

[kaipiyann]

Add _meta field to schema

Motivation and Context

Field meta from the spec is missing
https://modelcontextprotocol.io/specification/2025-06-18/basic#meta

How Has This Been Tested?

Tested with MCP Inspector

Breaking Changes

No

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[kaipiyann]

And this time I did run all the tests also so it should pass the check.

[chr-hertel]

I struggle a bit with adding meta also to the attributes - i consider meta rather decoupled from the core schema elements. What was your reasoning here?

[kaipiyann]

@chr-hertel I just need it. I tried to make MCP widget for Openai so I need to be able to define _meta for tool and ressource.
Doc : https://developers.openai.com/apps-sdk/build/mcp-server

[chr-hertel]

Works for me - thanks 👍

Requested changes have been applied

[chr-hertel]

@kaipiyann please squash your changes to a single signed commit

[kaipiyann]

@chr-hertel : Signed and squashed !