Allow custom annotation fields to pass through McpAnnotationMapper

[galatanovidiu]

Problem

McpAnnotationMapper::map() uses a strict whitelist of known MCP annotation fields (readOnlyHint, destructiveHint, idempotentHint, openWorldHint, audience, priority, title, lastModified). Any annotation key not in this list is silently discarded during the mapping from WordPress Abilities API to MCP tools.

This prevents consumers from attaching domain-specific metadata to tool annotations.

Compliant MCP clients will ignore fields they don't recognize, so passing through additional fields is protocol-safe.

Proposed Change

After mapping known MCP annotation fields, preserve any remaining keys from the source annotations array. Unknown fields should be included as-is in the mapped output.

[flodufour]

Hi @galatanovidiu,

I’m new to PHP and WordPress, and I’d love to take my first steps by working on this issue. Would it be possible to have it assigned to me?

I’ve already looked at the code and the related tests, and I wanted to confirm: is the intended behavior to pass through only unknown annotation fields, while still excluding known fields that are not applicable to the current feature type?

Thanks in advance!