1. Minimal JSON Shape (schema_version = 1)

Downlink EnvelopeJson allows omitting envelope meta information (Optional):

{
  "schema_version": 1,
  "event": { "kind": "write_point" },
  "payload": {
    "data": {
      "request_id": "req-123",
      "point_id": 10001,
      "value": 1,
      "timestamp": "2026-01-19T00:00:00Z",
      "timeout_ms": 5000
    }
  }
}

TIP

Parsing will first use event.kind for routing matching:

• kind mismatch → Directly ignore (Not treated as error)
• kind match but payload shape incorrect → Treated as "Decoding Error"

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2. Supported Downlink kind

• write_point
• command_received
• rpc_response_received

Different plugins support different ranges, please refer to plugin specific documentation.

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3. Production Suggestion

• One control plane topic carries only one kind: Simplest, least noise
• If mixing is necessary: EnvelopeJson is still usable because event.kind is routable

More strategies see: Downlink Overview