Custom event payload schemas

Custom events may be created without a schema. Schema-less events, including unknown event names that have not been created yet, keep accepting any object payload and can still record deliveries or trigger matching automations.

When a stored custom event has a schema, POST /api/events/send validates the payload before contact creation, delivery recording, waiting-run resume, or new automation-run creation. Invalid payloads return 422 with stable details entries that include field paths such as payload.plan.

Supported schema dialect

The first backend slice intentionally supports a narrow JSON-Schema-like object descriptor instead of adding a broad JSON Schema dependency:

{
  "type": "object",
  "required": ["plan", "trial"],
  "properties": {
    "plan": { "type": "string" },
    "seats": { "type": "number" },
    "trial": { "type": "boolean" },
    "metadata": {
      "type": "object",
      "required": ["source"],
      "properties": {
        "source": { "type": "string" }
      }
    }
  }
}

Supported property types are string, number, boolean, object, and array. Extra payload fields are allowed; the schema only constrains listed properties and required fields. Unsupported schema keywords are rejected when an event schema is created.