feat: add server capabilities schema for transport agnostic capability exchange#731
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gspencergoog merged 3 commits intogoogle:mainfrom Feb 27, 2026
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This pull request introduces a server_capabilities.json schema to make server capabilities transport-agnostic, along with updates to the documentation to reflect this change. The implementation is clear and aligns with the stated goals. I've provided a couple of suggestions to improve the precision of the new schema and the related documentation, which should enhance clarity for implementers.
gspencergoog
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Feb 27, 2026
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This PR introduces a 'server_capabilities.json' schema to A2UI v0.9 to make capabilities transport agnostic. It can be used by servers to declare their UI generation capabilities such as supported catalogs and inline catalog support.
This is motivated by improving the MCP story - see internal doc https://docs.google.com/document/d/1n6kQq0A2bd0o6UNVMUbVkYvsR3ljX3iH5kZNCB2XwCw/edit?resourcekey=0-0nfhkWbnRlMHPFEXHAEgCQ&tab=t.0
Updates:
server_capabilities.json.a2ui_extension_specification.mdto reference the new schema for A2A AgentCard params.a2ui_protocol.mdto explain how servers and clients exchange capabilities through transport metadata.