rohitg00/agentmemory · error · Error

Unknown method: ${method}

Error message

Unknown method: ${method}

What it means

The standalone MCP server's JSON-RPC message handler switches on the `method` field of incoming requests (initialize, tools/list, tools/call, etc.) and throws this for any method it does not implement. It is thrown synchronously out of the transport callback, so the client sees a protocol-level failure rather than a JSON-RPC error response with a proper code.

Source

Thrown at src/mcp/standalone.ts:512

      const toolName = params.name as string;
      const toolArgs = (params.arguments as Record<string, unknown>) || {};
      try {
        return await handleToolCall(toolName, toolArgs);
      } catch (err) {
        return {
          content: [
            {
              type: "text",
              text: `Error: ${err instanceof Error ? err.message : String(err)}`,
            },
          ],
          isError: true,
        };
      }
    }

    default:
      throw new Error(`Unknown method: ${method}`);
  }
});

process.stderr.write(
  `[@agentmemory/mcp] Standalone MCP server v${SERVER_INFO.version} starting...\n`,
);
transport.start();

process.on("SIGINT", () => {
  kv.persist();
  process.exit(0);
});
process.on("SIGTERM", () => {
  kv.persist();
  process.exit(0);
});

View on GitHub (pinned to e04ba88819)

Solutions

1. Only send methods this server implements: initialize, tools/list, tools/call (see the switch ending at standalone.ts:512).
2. Disable/disable-negotiate resources and prompts in the client for this server, or use the full agentmemory MCP server which supports them.
3. Check the exact method string casing/spelling in your JSON-RPC payload.
4. If you need the method, add a case to the transport switch in src/mcp/standalone.ts.

Example fix

// before
{ "jsonrpc": "2.0", "id": 2, "method": "resources/list" }
// after
{ "jsonrpc": "2.0", "id": 2, "method": "tools/list" }

const IMPLEMENTED_METHODS = new Set(["initialize", "tools/list", "tools/call"]);
function assertSupportedMethod(method: string) {
  if (!IMPLEMENTED_METHODS.has(method)) throw new Error(`Method "${method}" not implemented by standalone server`);
}

function isImplementedMethod(m: string): m is "initialize" | "tools/list" | "tools/call" {
  return m === "initialize" || m === "tools/list" || m === "tools/call";
}

try {
  await rpc(method, params);
} catch (e) {
  if (e instanceof Error && e.message.startsWith("Unknown method:")) {
    console.warn(`${method} unsupported; skipping`); // degrade to no-op
  } else throw e;
}

When it happens

Trigger: Sending a JSON-RPC request whose `method` is not one of the handled cases — e.g. `resources/list`, `prompts/list`, `ping`, or a notifications/... method when the client expects the standalone bundle to support it, or a misspelled method name.

Common situations: A generic MCP client negotiates capabilities (resources, prompts, sampling) that this minimal standalone server doesn't implement; hand-crafted curl/WebSocket JSON-RPC payloads with wrong method strings; protocol version drift where newer clients call methods this server predates.

Related errors

• mem::search: token_budget must be a positive integer
• Unknown tool: ${toolName}
• content is required
• query is required
• memoryIds is required

AI-assisted analysis of rohitg00/agentmemory@e04ba88819 (2026-08-30). Data as JSON: /api/errors/9f3a934900111101. Report an issue: GitHub.