Advertise the MCP Apps UI client capability in the inspector#87
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abewheel merged 1 commit intoJun 30, 2026
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The inspector connects to MCP servers without declaring capabilities.extensions["io.modelcontextprotocol/ui"]. Per the MCP Apps spec, the host advertises which UI resource MIME types it can render, and servers may gate inline UI rendering on that advertisement (returning a text or URL fallback to hosts that don't advertise). Since the inspector renders these resources, it should advertise that it can, otherwise such servers never return the ui:// resource and nothing renders.
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The inspector connects to MCP servers without declaring capabilities.extensions["io.modelcontextprotocol/ui"]. Per the MCP Apps spec, the host advertises which UI resource MIME types it can render, and servers may gate inline UI rendering on that advertisement (returning a text or URL fallback to hosts that don't advertise). Since the inspector renders these resources, it should advertise that it can, otherwise such servers never return the ui:// resource and nothing renders.