Discovery of Model Context Protocol Servers via DNS TXT Records vs MCP Server Cards (SEP-2127)
They sit at the same step and overlap in purpose; the fields above are the basis for choosing.
| Discovery of Model Context Protocol Servers via DNS TXT Records | MCP Server Cards (SEP-2127) Server Card | |
|---|---|---|
| Lifecycle step | 1 Discover: What is here, and where? | 1 Discover: What is here, and where? |
| Answers | How can a client discover an MCP server's endpoint, the operating organisation's identity, and a signed ~handle identity envelope using DNS TXT records under a domain? | How can a client learn what an MCP server offers before connecting to it? |
| Governed by | Individual Internet-Draft by a single author; not adopted by an IETF working group per the page text (Network Working Group, Intended Status: Informational). | Model Context Protocol project (SEP process, MCP governance) |
| Status (issuer's words) | Active Internet-Draft (-09, Informational; expires 2027-04-25) | SEP-2127 Final (2026-10-06), Extensions Track charter; the MCP Registry working group page still describes Server Cards as experimental |
| Version | draft-morrison-mcp-dns-discovery-09 (2026-10-22) | SEP-2127 (Final) (2026-10-06) |
| Form / transport | DNS record | document format |
| Found at | _mcp.<domain> | GET <streamable-http-url>/server-card |
| Implementation | none found | multi-implementation |
| Evidence | 1 reported, 1 verified | 7 verified, 1 reported |
| Primary use case | Let agents discover my API or service | Let agents discover my API or service |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://datatracker.ietf.org/doc/html/draft-morrison-mcp-dns-discovery-09 | https://github.com/modelcontextprotocol/modelcontextprotocol/blob/main/seps/2127-mcp-server-cards.md |
When to use which
- Choose Discovery of Model Context Protocol Servers via DNS TXT Records when your question is “How can a client discover an MCP server's endpoint, the operating organisation's identity, and a signed ~handle identity envelope using DNS TXT records under a domain?” and you accept its maturity: status "Active Internet-Draft (-09, Informational; expires 2027-04-25)", implementation none found.
- Choose MCP Server Cards (SEP-2127) when your question is “How can a client learn what an MCP server offers before connecting to it?” and you accept its maturity: status "SEP-2127 Final (2026-10-06), Extensions Track charter; the MCP Registry working group page still describes Server Cards as experimental", implementation multi-implementation.
Read the full articles
- Discovery of Model Context Protocol Servers via DNS TXT Records: How can a client discover an MCP server's endpoint, the operating organisation's identity, and a signed ~handle identity envelope using DNS TXT records under a domain?
- MCP Server Cards (SEP-2127): How can a client learn what an MCP server offers before connecting to it?