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MCP Server Contract Tester — stdio + WebSocket Transports, JSON Schema 2020-12 Tool Validation

End-to-end Model Context Protocol contract testing: JSON-RPC 2.0 initialize handshake and version negotiation over stdio (newline-delimited) and WebSocket (one message per text frame), tools/list inputSchema object-root and draft 2020-12 compilation, resources/list + read, prompts/list + get, ping, -32601 error semantics, sampling/createMessage round-trip, and framing discipline — with an embedded reference server for offline self-verification.

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Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'http://127.0.0.1:3003/en/api/tools/model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester' \
  -H 'Content-Type: application/json' \
  -d '{"mode":"reference-selftest","serverCommand":"","wsUrl":"","protocolVersion":"2025-06-18","requestTimeoutMs":5000,"validateSchemas":true}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST http://127.0.0.1:3003/en/api/tools/model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester

Parameters

Name	Type	Required	Description
mode	select	Yes	—
serverCommand	text	No	—
wsUrl	text	No	—
protocolVersion	select	No	—
requestTimeoutMs	number	No	—

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester": {
      "name": "model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester",
      "description": "End-to-end Model Context Protocol contract testing: JSON-RPC 2.0 initialize handshake and version negotiation over stdio (newline-delimited) and WebSocket (one message per text frame), tools/list inputSchema object-root and draft 2020-12 compilation, resources/list + read, prompts/list + get, ping, -32601 error semantics, sampling/createMessage round-trip, and framing discipline — with an embedded reference server for offline self-verification.",
      "baseUrl": "http://127.0.0.1:3003/mcp/sse?toolId=model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "model-context-protocol-mcp-server-tool-schema-stdio-websocket-transport-contract-tester",
    "arguments": {
  "mode": "reference-selftest",
  "serverCommand": "",
  "wsUrl": "",
  "protocolVersion": "2025-06-18",
  "requestTimeoutMs": 5000,
  "validateSchemas": true
}
  }
}

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