Discovery

server/discover lets a client query a server’s supported protocol versions, capabilities, and identity before sending any other requests. Servers MUST implement it.

Request

The request carries no body parameters beyond the standard _meta:

{
  "jsonrpc": "2.0",
  "id": "discover-1",
  "method": "server/discover",
  "params": {
    "_meta": {
      "io.modelcontextprotocol/protocolVersion": "2026-07-28",
      "io.modelcontextprotocol/clientInfo": {
        "name": "ExampleClient",
        "version": "1.0.0"
      },
      "io.modelcontextprotocol/clientCapabilities": {}
    }
  }
}

Response

The server replies with its supported protocol versions, capabilities, and identity. This operation supports caching.

{
  "jsonrpc": "2.0",
  "id": "discover-1",
  "result": {
    "resultType": "complete",
    "supportedVersions": ["2026-07-28"],
    "capabilities": {
      "tools": {},
      "resources": {}
    },
    "_meta": {
      "io.modelcontextprotocol/serverInfo": {
        "name": "ExampleServer",
        "version": "1.0.0"
      }
    },
    "instructions": "This server provides weather and resource utilities.",
    "ttlMs": 3600000,
    "cacheScope": "public"
  }
}

When to Call

Calling server/discover is optional for clients — a client may invoke any RPC inline and handle UnsupportedProtocolVersionError if the server does not support the requested version. However, server/discover is useful in two scenarios:

• Presenting server information. While a client doesn’t need to call server/discover to use the server, it’s a convenient way to retrieve the server’s identity, capabilities, and supported versions in a single request. For example, a client can present the capabilities a server supports from a single server/discover response instead of probing with separate tools/list, prompts/list, and resources/list requests.
• stdio backward-compatibility probe. On stdio, there is no per-request HTTP status code to drive fallback. A client that supports both modern (per-request _meta) and legacy (initialize handshake) servers SHOULD send server/discover first; see stdio: Backward Compatibility for the fallback rules.

See Protocol Version Negotiation for the full version-selection flow. For HTTP-specific status codes returned for unknown methods, see the Protocol Version Header section in Transports.

Data Types

DiscoverResult

A discovery result includes:

• supportedVersions: Protocol versions the server supports. The client should choose one of these for subsequent requests.
• capabilities: Capabilities the server supports (tools, resources, prompts, etc.)
• _meta['io.modelcontextprotocol/serverInfo']: Name and version of the server software. Servers SHOULD include this field.
• instructions: Optional natural-language guidance for LLMs on how to use this server effectively

serverInfo is self-reported by the server and is not verified by the protocol. It is intended for display, logging, and debugging. Clients SHOULD NOT use it to change their behavior, and SHOULD NOT rely on it for security decisions.