Describe the bug
The _meta property on CallToolResult has the description "This result property is reserved by the protocol to allow clients and servers to attach additional metadata to their responses." - "reserved" is generally used in specs to imply that the spec is reserving this for future definition, but I don't think that's actually correct here, I think this is meant as a free form field. The question would be - is that "reserved" in the traditional sense or is it fine to start using this today?

To Reproduce
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Expected behavior
I would clarify the description to say "The result property is available for server to client communication of arbitrary data which falls outside the scope of this specification"

Logs
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Additional context
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