Agent ExplorerBeta

Payload Builder

The Payload Builder provides a structured UI for constructing valid A2A JSON-RPC message payloads without needing to write raw JSON.

The Chat tab on a mock agent with a sent message and echoed response

Accessing the Builder

  1. Open an agent from the Explorer
  2. Go to the Chat tab
  3. Use the advanced input options or the Payload Builder button in the toolbar

Building a Message

Basic Fields

  • Message ID — Auto-generated UUID (editable if needed)
  • Role — Always "user" for outgoing messages

Adding Parts

Click Add Part and choose a type:

Part TypeUse Case
TextPlain text content, the most common type
FileBinary file attachments (base64 encoded)
DataStructured JSON data payloads

Text Part

{ "kind": "text", "text": "Your message here" }

File Part

{
  "kind": "file",
  "file": {
    "name": "example.txt",
    "mimeType": "text/plain",
    "bytes": "SGVsbG8gV29ybGQ="
  }
}

Data Part

{
  "kind": "data",
  "data": { "customField": "value" }
}

Templates

Save frequently-used payloads as templates and reload them quickly:

  1. Build your payload
  2. Click Save as Template
  3. Give it a name
  4. Load it again from the Templates dropdown

Preview & Send

  1. Click Preview to see the full JSON-RPC envelope
  2. Verify the structure
  3. Click Send to execute the request

The response appears in the conversation view alongside the task state.