JSON-RPC Builder — Compose and Validate JSON-RPC 2.0 Payloads

How to Use the JSON-RPC Request Builder:

1. Load a Preset (Optional): Click any preset to pre-fill all fields with a real-world JSON-RPC 2.0 example. Simple call shows a named-params request. Positional params demonstrates array-style params. No params builds a call without a params field. Notification shows a fire-and-forget call with no id. Batch shows how to combine multiple calls into a single HTTP request array. All presets can be edited after loading.

2. Choose the Request Type: The Type selector offers three modes. Request is the standard call-and-response pattern where the server returns a matching response keyed by the id. Notification is a fire-and-forget message — the id field is omitted and the server sends no response. Batch lets you paste one JSON-RPC object per line; the tool wraps them into an array and generates a single curl command that sends all calls at once.

3. Enter the Method Name: The method field is required. It must be a non-empty string with no spaces. Method names starting with rpc. (for example rpc.discover) are reserved by the JSON-RPC 2.0 specification for internal use and are rejected. Conventionally, methods use dot notation to namespace them: user.getProfile, payments.refund, math.subtract.

4. Enter Params (Optional): Paste a JSON object for named params ({"userId": "abc"}) or a JSON array for positional params ([42, 23]). The field is optional — if left empty, the params field is omitted from the payload entirely, which is spec-compliant. Invalid JSON triggers an inline error and blocks payload generation.

5. Configure the ID: For Request type, choose whether the id should be a number (most common), a string, or null. A null id is technically valid under the spec but is discouraged because it is indistinguishable from a notification in some implementations. The id is omitted automatically for Notification type.

6. Set the Endpoint URL: Enter the URL of the JSON-RPC endpoint you want to call. This is only used to generate the curl command — it does not affect the JSON payload itself. Leave the default placeholder if you only need the payload.

7. Read the Output: The right panel shows the formatted payload in real time. Switch to the curl tab to see a complete curl command ready to paste into a terminal. Both outputs can be copied individually using the Copy payload and Copy curl buttons at the bottom.

8. Fix Validation Errors: Any spec violation (missing method, invalid JSON params, reserved method name) displays a red inline error under the affected field. The payload output is hidden until all errors are resolved.

Common Use Cases:

• Manual API testing: Build a payload and run it with curl before writing client code, to confirm the server accepts the call shape.
• JSON-RPC endpoint development: Quickly generate valid request shapes to test new server-side method handlers during development.
• Learning JSON-RPC 2.0: Use the presets to explore the difference between requests, notifications, and batch calls without reading the spec from scratch.
• Debugging existing integrations: Re-build a known-good payload in the builder and compare it to what your client is sending to spot field-level differences.
• Batch operation testing: Compose multi-method batch arrays to test server-side batch handling and response ordering.

Tips and Best Practices:

• Prefer named params (JSON objects) over positional params (arrays) for methods with more than two arguments — they are easier to maintain and extend.
• The id field is what the server echoes back in its response to match requests and responses. Use a unique id per in-flight request when making concurrent calls.
• A notification (no id) is appropriate for logging, telemetry, and event reporting where you do not need a success or error confirmation.
• JSON-RPC 2.0 always requires "jsonrpc": "2.0" — the builder adds this automatically.
• Batch responses may arrive in any order and may omit responses for notifications in the batch. Match each response to its request using the id field.