MCP defines how AI agents connect to tools. It says nothing about how agents discover which tools exist. Without a discovery layer: n agents × m servers = n×m manual configuration decisions. With a registry: n+m.

The proposal: publish a single _mcp TXT record at your domain. Any compliant agent resolves it and finds your entire MCP ecosystem — no central directory, no SDK, no new protocol. The registry is itself an MCP server, so discovery uses the same tools/list call agents already make. Zero new client behaviour required.

You can verify the live DNS record right now: dig TXT _mcp.mariothomas.com +short

Three servers registered: articles and locations (public), documents (authenticated — demonstrates the governance pattern). All endpoints speak JSON-RPC 2.0 over HTTPS.

Architecture paper, full spec, and CloudFormation template: github.com/mariothomas/mcp-dns-registry Deployed on Lambda@Edge and DynamoDB. Costs under $5/month to run. Took one day to deploy. A discussion is open in the MCP GitHub repository if anyone wants to engage on the proposal formally.