JSON-RPC Request Builder

What it does

Construct valid JSON-RPC 2.0 messages - requests, notifications (no id), success responses, and error responses - and validate their structure. Includes the standard error codes (-32700 … -32000). Paste an existing message to load it back into the editor. 100% client-side.

How to use it

1. Pick a Message type (Request / Notification / Result / Error), or start from a preset: initialize, tools/call, notify.
2. Fill the relevant fields (method/params/id/result/error code).
3. Watch the live output on the right; Copy or Download it as request.json.
4. Paste an existing JSON-RPC message via Paste an existing message to round-trip it into the editor.
5. The URL always carries your current message - copy it to share or bookmark the exact state.

Examples

tools/call preset (method tools/call, params {"name":"get_weather","arguments":{"city":"Paris"}}, id 2) →

{
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "name": "get_weather",
    "arguments": { "city": "Paris" }
  },
  "id": 2
}

The notify preset builds a notification - a method message with no id, so the peer never replies:

{
  "jsonrpc": "2.0",
  "method": "notifications/initialized",
  "params": {}
}

Good to know

• Private: generation is local.
• Notices: scalar params (spec wants an array or object) and a cleared id on a request (the peer cannot reply) surface as badges next to the output.
• Empty params text omits the params member; text that is not valid JSON is kept as a string parameter so your edit is never lost.
• Error messages use the standard text when you don’t supply one; unknown codes fall back to -32603 (internal error).
• Related tools: JSON Formatter, JSON to SQL.