c9d36b04bf
Three pages carried names the 2026-07-28 specification does not use: "Multi-Round-Trip Results" for the pattern the specification titles Multi Round-Trip Requests (MRTR) and serves at basic/patterns/mrtr - the results are the `InputRequiredResult` wire type, not the feature - plus "Completions" for the utility the specification titles Completion, and "Notification Subscriptions" for the pattern it titles Subscriptions. Retitle the three pages to the specification's names, move them to /server/mrtr/ and /client/mrtr/, /server/completion/, and /server/subscriptions/ following the specification's slugs, update every internal reference, and keep the URLs published with v1.3.0 working via jekyll-redirect-from. The Discovery page keeps its title but moves from /server/discovery/ to /server/discover/, matching the specification's slug and the `server/discover` RPC, with its published URL redirected the same way.
2.5 KiB
| layout | title | nav_order | redirect_from | |
|---|---|---|---|---|
| default | Discovery | 3 |
|
Discovery
server/discover is the sessionless capability discovery method of MCP 2026-07-28 (SEP-2575).
It responds before initialize and without an Mcp-Session-Id, so a client learns what a server
offers in a single exchange, without creating a session.
The Discovery Result
The result carries the modern supportedVersions, capabilities, and instructions, together with
the required ttlMs/cacheScope cache hints, and the server identity as the optional
io.modelcontextprotocol/serverInfo stamp in the result _meta.
The request takes no parameters:
{ "jsonrpc": "2.0", "id": 1, "method": "server/discover" }
The server answers with the full discovery result:
{
"jsonrpc": "2.0",
"id": 1,
"result": {
"supportedVersions": ["2026-07-28"],
"capabilities": { "tools": { "listChanged": true } },
"instructions": "Use the tools of this server as a last resort",
"_meta": { "io.modelcontextprotocol/serverInfo": { "name": "my_server", "version": "1.0.0" } },
"ttlMs": 0,
"cacheScope": "private",
"resultType": "complete"
}
}
The Stateless Modern Lifecycle
Beyond answering server/discover, the server serves the full stateless modern lifecycle: requests carrying the SEP-2575 _meta envelope
(io.modelcontextprotocol/protocolVersion, clientInfo, and clientCapabilities) are validated per request,
and the Streamable HTTP transport serves them on a sessionless single-exchange path.
Calling server/discover first is not required: the envelope alone selects the modern lifecycle for a request,
while a client performing the classic initialize handshake is served on the handshake lifecycle -
the lifecycle is a per-request property, not a server-wide mode.
The bundled transports serve server/discover and the per-request _meta envelope alongside the initialize handshake
with no configuration needed. The protocol_version pin scopes the handshake only
and does not affect the modern lifecycle; see Configuration for details.
Client Side
On the client, MCP::Client#connect negotiates the lifecycle automatically by default
(probe server/discover, fall back to the initialize handshake), connect(mode: :modern) skips
the handshake entirely, connect(mode: :legacy) forces the classic handshake, and MCP::Client#discover
exposes the raw discovery result. See the client-side Lifecycle page for details.