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mcp: update return meta in DiscoverResult (SEP-2575) (#1097)

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This PR implements the latest changes introduced by
https://github.com/modelcontextprotocol/modelcontextprotocol/pull/3002
This commit is contained in:
Guglielmo Colombo 2026-07-16 16:10:12 +02:00 • committed by GitHub
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37
internal/docs/protocol.src.md
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@ -17,8 +17,10 @@ transparently based on the negotiated protocol version:
- A **stateless** model introduced in `2026-07-28` by
[SEP-2575](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2575),
in which there is no `initialize`/`notifications/initialized` handshake, and
each request carries its protocol version, client identity, and client
capabilities in `_meta`.
each request carries its protocol version and client capabilities in
`_meta`. Clients SHOULD also include their identity (`clientInfo`) on every
request, and servers SHOULD include their identity (`serverInfo`) on every
response.
In both models, the SDK exposes the same API:
@ -76,17 +78,28 @@ When the negotiated protocol version is `2026-07-28` or later, every request
carries these keys inside its `_meta` map (constants live in
[`mcp/protocol.go`](https://pkg.go.dev/github.com/modelcontextprotocol/go-sdk/mcp#pkg-constants)):
| Constant | Wire key | Type |
|---|---|---|
| `MetaKeyProtocolVersion` | `io.modelcontextprotocol/protocolVersion` | `string` |
| `MetaKeyClientInfo` | `io.modelcontextprotocol/clientInfo` | `*Implementation` |
| `MetaKeyClientCapabilities` | `io.modelcontextprotocol/clientCapabilities` | `*ClientCapabilities` |
| `MetaKeyLogLevel` | `io.modelcontextprotocol/logLevel` | `LoggingLevel` (deprecated by SEP-2577) |
| Constant | Wire key | Type | Required |
|---|---|---|---|
| `MetaKeyProtocolVersion` | `io.modelcontextprotocol/protocolVersion` | `string` | Yes |
| `MetaKeyClientCapabilities` | `io.modelcontextprotocol/clientCapabilities` | `*ClientCapabilities` | Yes |
| `MetaKeyClientInfo` | `io.modelcontextprotocol/clientInfo` | `*Implementation` | No |
| `MetaKeyLogLevel` | `io.modelcontextprotocol/logLevel` | `LoggingLevel` (deprecated by SEP-2577) | No |
The client populates these keys automatically on every outgoing request.
Server-side handlers can read them
through `ServerRequest[P].ProtocolVersion()`, `ServerRequest[P].ClientInfo()`,
and `ServerRequest[P].ClientCapabilities()`.
The client populates the required keys automatically on every outgoing
request, and populates `clientInfo` when configured with an `*Implementation`
(the default). Server-side handlers can read them through
`ServerRequest[P].ProtocolVersion()`, `ServerRequest[P].ClientInfo()`, and
`ServerRequest[P].ClientCapabilities()`.
### Per-response `_meta` keys
Under the same protocol version, servers SHOULD identify themselves on every
response. The SDK populates this
key automatically on every outgoing response:
| Constant | Wire key | Type | Required |
|---|---|---|---|
| `MetaKeyServerInfo` | `io.modelcontextprotocol/serverInfo` | `*Implementation` | No |
### Subscriptions (`subscriptions/listen`)