Inspect MCP extension capability declarations and check extension identifiers for the expected vendor-prefix/name structure.
MCP 2026-07-28 formalized protocol extensions. Extension identifiers use vendor namespaces so independent capabilities can evolve outside the core specification without colliding.
Validate MCP extension declarations, reverse-DNS identifiers and extension capability maps.
Use MCP Extension Declaration Validator as a focused pre-flight utility while building, reviewing or debugging an MCP integration. Paste the relevant configuration, protocol message, metadata, schema or value into the tool and review the returned findings before the same data reaches a production client or server.
Extensions add optional behavior outside the MCP core. Both sides should explicitly support the extension being used, and extension-specific data should be validated separately from the base protocol envelope.
A clean result means the input passed the rules implemented by this utility. It does not guarantee application security, protocol interoperability or correct business behavior. Test important integrations against the exact MCP client, SDK, gateway and server versions used in your deployment.