---
title: AgentDeclaration
description: "What `agent()` takes: an `AgentDefinition`, except that `model` can also be `open`."
---

# `AgentDeclaration`

Type, in `@jr2/orchestrator/src/agent.ts`. The signature of an export, or a type that it names, names this type. The [Authoring surface](../authoring-surface.md) page lists each export. This type is not an export of `@jr2/orchestrator`, so a workflow module does not import it by name.

```ts
type AgentDeclaration = Omit<AgentDefinition, "model"> & {
  model: string | typeof open;
};
```

What `agent()` takes: an [`AgentDefinition`](type-agentdefinition.md), except that `model` can also be `open`.

**Fields**: each field of [`AgentDefinition`](type-agentdefinition.md), except `model`, and these:

- `model`: `string | typeof open`

  The model, as `<provider>/<modelId>`: for example `anthropic/claude-haiku-5-5`. Required:
  there is no default model. The provider must be one that `jr2.config.ts` can reach.

  Or `open`, in a Machine that you publish as a package. Then the Instance that registers the
  Machine binds the model with `customize()`. One Turn may set another model in the invoke's
  `input`.