"OpenTimestamps - Bitcoin-based timestamping protocol" matching MCP connectors:

Developer checks and Agent Observatory: A2A, MCP and OpenAPI checks with a dated change log.

Check public MCP reachability, protocol handshake, auth and tool schemas before connecting.

Grafbase

com.grafbase.api

The Grafbase MCP server sits in front of a GraphQL API and exposes an MCP protocol-compliant interface that allows AI agents and LLMs to explore and query GraphQL APIs using natural language. It provides tools to search schemas, introspect types and fields, and execute GraphQL queries while minimizing context bloat by returning only relevant schema subsets, with built-in support for authentication, authorization, and configurable access control.