Copyable example

Use server/discover without rebuilding initialize.

For MCP protocol revision 2026-07-28

server/discover lets a client learn supported versions and server capabilities. It is a lightweight discovery call, not a stateful handshake. Servers implement it; clients may skip it when they already know the target version.

Request

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

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "supportedVersions": ["2026-07-28", "2025-11-25"],
    "capabilities": {
      "tools": {}
    },
    "instructions": "Use the tools to inspect build artifacts."
  }
}

Implementation notes

• supportedVersions is an array because one endpoint may support a current stateless revision and a legacy fallback.
• capabilities describes the server, while request metadata describes capabilities available from this client for this call.
• Instructions should add useful operating context rather than duplicate every tool description.
• For HTTP, send the same version in MCP-Protocol-Version.

Common mistakes

Do not return a session ID, treat discovery as authorization, omit request metadata, or make all later requests depend on server-side state created by discovery. Check a complete exchange in the free stateless validator.