Mock MCP servers for testing agents and MCP clients

What a mock MCP server does

A mock MCP server is a temporary Model Context Protocol endpoint whose tools return text you configure. Use it to test how an agent or MCP client discovers tools, validates arguments, handles tool errors and copes with latency, without building a real server. Tools never execute code; each call returns its configured response.

Create a server

POST /api/mcp-servers with a name (up to 80 characters) and 1 to 10 tools. Query parameters set visibility, ttlSeconds and persistent as for other resources. The response includes endpointUrl, a managementToken and, for private servers, an accessToken.

curl -X POST https://socket.help/api/mcp-servers \
  -H 'Content-Type: application/json' \
  -d '{
    "name": "Weather",
    "tools": [{
      "name": "get_forecast",
      "description": "Return a forecast for a city.",
      "inputSchema": {
        "type": "object",
        "properties": { "city": { "type": "string" } },
        "required": ["city"]
      },
      "response": "Sunny, 21 degrees",
      "delayMs": 500
    }]
  }'

# 201 Created
{
  "id": "SERVER_ID",
  "managementToken": "MANAGEMENT_TOKEN",
  "expiresAt": "2026-10-27T13:00:00.000Z",
  "visibility": "private",
  "accessVersion": "ACCESS_VERSION",
  "accessToken": "ACCESS_TOKEN",
  "endpointUrl": "https://socket.help/mcp/mock/SERVER_ID"
}

Tool fields

The whole configuration must fit in 80 KiB.

Connect a client

The endpoint speaks Streamable HTTP over POST and returns JSON responses. Clients must send Accept: application/json, text/event-stream. GET returns 405: SSE streams and transport sessions are not provided. Supported protocol versions are 2025-11-25, 2025-06-18 and 2025-03-26.

Supported methods are initialize, ping, tools/list and tools/call. Calls are checked against the tool’s schema: missing required arguments, unknown arguments and wrong types return JSON-RPC error -32602. Notifications (requests without an id) get 202.

For a private server, send the access token in X-Access-Token or Authorization: Bearer on every request. Each server accepts up to 120 requests per minute.

curl https://socket.help/mcp/mock/SERVER_ID \
  -H "X-Access-Token: $ACCESS_TOKEN" \
  -H 'Accept: application/json, text/event-stream' \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call",
       "params":{"name":"get_forecast","arguments":{"city":"Paris"}}}'

{"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"Sunny, 21 degrees"}],"isError":false}}

Read, update and delete

GET /api/mcp-servers/{id} returns the configuration, visibility, accessVersion, expiresAt, uses and endpointUrl. PUT replaces the configuration and returns 204. DELETE removes the server immediately. Use the management token for anonymous servers and your API key for workspace servers.