TencentCloud/TencentDB-Agent-Memory · error

Unknown tool: ${name}

Error message

Unknown tool: ${name}

What it means

The MCP server's tool-call handler looks up request.params.name in toolMap, which is built from the registered tool endpoints. If the requested tool name is not registered, the handler logs a warning and returns an isError result with text 'Unknown tool: <name>' instead of throwing — the error text is the tool-call result returned to the MCP client.

Source

Thrown at MemoryKnowledge/src/mcp/server.ts:57

  server.setRequestHandler(ListToolsRequestSchema, async () => {
    return {
      tools: MCP_TOOLS.map((t) => ({
        name: t.name,
        description: t.description,
        inputSchema: t.inputSchema,
      })),
    };
  });

  // Call tool
  server.setRequestHandler(CallToolRequestSchema, async (request) => {
    const { name, arguments: args } = request.params;
    const tool = toolMap.get(name);
    if (!tool) {
      log.warn(`Unknown tool requested: "${name}"`);
      return {
        content: [{ type: "text", text: `Unknown tool: ${name}` }],
        isError: true,
      };
    }

    const body = (args ?? {}) as Record<string, unknown>;
    try {
      const data = await callApi(httpOpts, tool.endpoint, body);

      // The code-graph query endpoints return {text, isError} — pass through directly
      if (data && typeof data === "object" && "text" in data && "isError" in data) {
        const result = data as { text: string; isError: boolean };
        return {
          content: [{ type: "text", text: result.text || "(empty result)" }],
          isError: result.isError,
        };
      }

      // Other endpoints return structured data — serialize as JSON
      return {

View on GitHub (pinned to 3efcd317b8)

Solutions

1. Call tools/list on the server and use an exact name from the response
2. Fix the tool name spelling in the client request
3. Restart/refresh the client so it re-fetches the current tool list
4. If the tool should exist, register it in createMcpServer so it lands in toolMap

Example fix

// before
await client.callTool({ name: 'searchKnowledgebase', arguments: { q: 'x' } });
// after
const { tools } = await client.listTools();
await client.callTool({ name: 'search_knowledge_base', arguments: { q: 'x' } });

const { tools } = await client.listTools();
if (!tools.some(t => t.name === toolName)) throw new Error(`Tool "${toolName}" not registered on this server`);

function isRegisteredTool(name: string, tools: { name: string }[]): name is string {
  return tools.some(t => t.name === name);
}

const result = await client.callTool({ name, arguments: args });
if (result.isError && result.content?.[0]?.text?.startsWith('Unknown tool:')) {
  const { tools } = await client.listTools();
  console.error(`"${name}" not found. Available: ${tools.map(t => t.name).join(', ')}`);
}

When it happens

Trigger: A client sends tools/call with a name that is not in toolMap: typo in tool name, client cached a stale tool list after server tool set changed, or the tool was removed/renamed in server.ts while the client still references the old name.

Common situations: Client connected to an older server version exposing different tool names; hand-written MCP client calls with a mistyped tool name; multiple MCP servers running and the client sends a tool from one server to another.

Related errors

• ${TAG} ${path} envelope error ${env.code}: ${env.message ??
• Backend API error ${res.statusCode}: ${data}

AI-assisted analysis of TencentCloud/TencentDB-Agent-Memory@3efcd317b8 (2026-09-01). Data as JSON: /api/errors/79576ad3c1c947e2. Report an issue: GitHub.