## Add an assignment to a variation

`agents.variations.add_assignment(variation_id, **kwargs) -> VariationAssignment`

**post** `/v1/workspaces/{workspaceId}/agents/{agentId}/variations/{variationId}/assignments`

Assigns a tool, tool set, or sub-agent to a variation. Exactly one target ID must be set.

### Parameters

- `workspace_id: String`

- `agent_id: String`

- `variation_id: String`

- `sub_agent_id: String`

- `tool_id: String`

- `tool_set_id: String`

### Returns

- `class VariationAssignment`

  A read-only reference to a single tool, tool set, or sub-agent attached to
  a variation. Read the full set of assignments via `AgentVariationInfo.assignments`;
  mutations go through the dedicated add/remove assignment endpoints.

  The `id` identifies the assignment itself (not the referenced resource) and
  is the handle used to remove the assignment. It is returned by the add
  endpoint and present on every entry in `AgentVariationInfo.assignments`.

  - `id: String`

  - `agent: BareMetadata`

    BareMetadata contains the minimal metadata for a resource: the ID and an
    optional human-readable name. These are used for reference fields where the
    full metadata (account scoping, timestamps, labels, external IDs) is not
    needed — e.g., the tool references inside an agent variation spec or the
    tools assigned to an objective. Both fields are server-populated; clients
    provide IDs through sibling fields rather than by constructing a
    BareMetadata themselves.

    - `id: String`

    - `name: String`

      Human-readable name of the referenced resource, populated by the server
      on reads for convenience. Absent on references to resources that do not
      have a name (e.g., objective tasks).

  - `tool: BareMetadata`

    BareMetadata contains the minimal metadata for a resource: the ID and an
    optional human-readable name. These are used for reference fields where the
    full metadata (account scoping, timestamps, labels, external IDs) is not
    needed — e.g., the tool references inside an agent variation spec or the
    tools assigned to an objective. Both fields are server-populated; clients
    provide IDs through sibling fields rather than by constructing a
    BareMetadata themselves.

  - `tool_set: BareMetadata`

    BareMetadata contains the minimal metadata for a resource: the ID and an
    optional human-readable name. These are used for reference fields where the
    full metadata (account scoping, timestamps, labels, external IDs) is not
    needed — e.g., the tool references inside an agent variation spec or the
    tools assigned to an objective. Both fields are server-populated; clients
    provide IDs through sibling fields rather than by constructing a
    BareMetadata themselves.

### Example

```ruby
require "cadenya"

cadenya = Cadenya::Client.new(api_key: "My API Key")

variation_assignment = cadenya.agents.variations.add_assignment("variationId", workspace_id: "workspaceId", agent_id: "agentId")

puts(variation_assignment)
```

#### Response

```json
{
  "id": "id",
  "agent": {
    "id": "id",
    "name": "name"
  },
  "tool": {
    "id": "id",
    "name": "name"
  },
  "toolSet": {
    "id": "id",
    "name": "name"
  }
}
```