Discovery of Model Context Protocol Servers via DNS TXT Records (draft-morrison-mcp-dns-discovery-09)

Abstract

This document defines a DNS-based mechanism for discovering Model Context Protocol (MCP) servers, the identity of the organisations that operate them, and a cryptographic identity envelope bound to an individual Sovereign-tier ~handle published under the same zone. Three TXT records are defined. _mcp.<domain> advertises an MCP server's endpoint URL, agent protocol family, transport binding, cryptographic identity, and capability profile. _org-alter.<domain> advertises the operator's canonical organisational identity, including its legal entity, registry identifier, regions of operation, and any regulatory framework under which it must refuse external automated access. _alter.<domain> publishes an Ed25519-signed envelope binding a ~handle to a public key, an IdentityLog root reference, and a revocation commitment. DNSSEC validation is REQUIRED for the envelope record, and a DANE TLSA pin on the MCP endpoint is REQUIRED where resolving an envelope and opening an MCP session are one recognition transaction. The mechanism complements HTTPS-based discovery, and follows the precedent set by DKIM, SPF, DMARC, and MTA-STS. A companion alter: URI scheme is provisionally registered with IANA.