Describe an event type
describe_event_type reads an event type’s real schema from the store — every property with its JSON type and a suggested C# type. It is the grounding primitive the other design-time tools build on: any generated projection, read model, or spec starts from the fields the event actually carries, not a guess.
When to use it
Section titled “When to use it”- Before generating anything from an event type, to confirm its shape.
- To answer “what fields does
UserRegisteredhave?” without opening source code. - As the first step when an agent maps a natural-language request onto concrete events.
Parameters
Section titled “Parameters”| Parameter | Required | Description |
|---|---|---|
eventType | yes | The event type id/name to describe (for example UserRegistered). |
generation | no | A specific generation to describe. The latest is used when omitted. |
eventStore | no | The event store. Defaults to the configured event store. |
What it returns
Section titled “What it returns”The event type’s identity (id, generation, owner, source, whether it is a tombstone, and the originating store when it is a foreign type received through the inbox), plus a list of properties. Each property carries its name, JSON schema type, a suggested C# type, any schema format, whether it is required, and its description.
Returns null when no matching event type is registered — a signal that the name is wrong or the type has not been registered yet.
Example
Section titled “Example”Prompt: “What does the UserRegistered event look like?”
The agent calls describe_event_type with eventType: "UserRegistered" and gets back the grounded shape:
| Property | JSON type | C# type | Required |
|---|---|---|---|
Email | string | string | yes |
Name | string | string | no |
RegisteredAt | string (date-time) | DateTimeOffset | no |
The C# type suggestions map JSON schema types and formats to idiomatic C# — guid/uuid to Guid, date-time to DateTimeOffset, integer to int, arrays to IEnumerable<T>, and so on.
Related
Section titled “Related”- Read-model scaffolding uses these fields to build a read model.
- Event catalog returns the same field detail for every event type at once.