What is an MCP server card?
An MCP server card is a small public JSON document that describes a remote MCP server before anyone connects to it: its name, version, description, endpoint URLs and the protocol versions it supports. It became an official MCP extension with SEP-2127, which reserves your MCP URL plus /server-card as the recommended place for the card and uses an AI Catalog at /.well-known/ai-catalog.json for discovery from your domain.
From our data: As of 3 Nov 2026, 90 of the 214 software vendors in our rankings run a remote MCP server, and 17 still publish a file at /.well-known/mcp.json, the path from an earlier proposal.
Where it goes
The card: your MCP URL plus /server-card
For a server at https://mcp.example.com/mcp, that's https://mcp.example.com/mcp/server-card. Cards may live at any URL; this one is reserved as the recommended spot.
The catalog: /.well-known/ai-catalog.json
An AI Catalog on your main domain links to or embeds the cards for your agent-facing services, so a client that only knows example.com can find them. It can also cover servers that a platform hosts for you.
Not /.well-known/mcp.json
That path came from an earlier proposal (issue #1649). It isn't the accepted design, though some sites still publish it.
What's in a card, and what isn't
Identity (name, version, description, and optionally a title, icons, repository and website), the remote endpoints with any headers or URL variables, the protocol versions they support, and optional namespaced _meta.
No tools, resources or prompts. Those can change per user and per deployment, so clients still list them live after connecting. The card also doesn't advertise capabilities. The exact schema is maintained in the modelcontextprotocol/experimental-ext-server-card repository; copy field names from there, not from older blog posts.
Server cards, server/discover and server.json
A server card is static, public and cacheable: it tells a client a server exists and how to reach it. server/discover, added in the 2026-07-28 spec, returns the same kind of information live once a client connects; if the two disagree, clients should trust the live answer. The MCP Registry's server.json is a separate format for registry entries, including local packages.
Check it yourself
Both should return JSON with a 200. Cards are public metadata, so it's fine to serve them with Access-Control-Allow-Origin: * and normal cache headers. Never put credentials or per-user data in them.
curl -s https://mcp.example.com/mcp/server-card curl -s https://example.com/.well-known/ai-catalog.json
Questions
Do I need an MCP server card?
No. Cards are an optional extension; your server works without one. They help registries, IDEs and agents find and configure your server automatically.
Can a server card list my tools?
No. SEP-2127 leaves tools, resources and prompts out on purpose, because they vary by user and deployment. Clients get them live with tools/list.
Is /.well-known/mcp.json still valid?
It was proposed earlier but isn't the accepted design. Use /server-card on your MCP URL and an AI Catalog at /.well-known/ai-catalog.json.