> ## Documentation Index
> Fetch the complete documentation index at: https://docs.automate.ax/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Automate.ax automations are TypeScript programs.
> Use Bun for installation and command examples.
> Use Automate.ax for the product name and automate.ax for the package, CLI, and domain.
> Treat documented public APIs as current; do not invent transitional or deprecated names.

# Add card label

> Apply one existing board label to a Trello card.

`addCardLabel` applies a reusable label and returns the refreshed card.

```ts automations/label-trello-card.automation.ts theme={null}
import { automation, onHttpRequest } from "automate.ax"
import { addCardLabel } from "automate.ax/trello"

export default automation("Label Trello card", () => {
  onHttpRequest({ scope: "automation" })
  addCardLabel({ card: "card-id", labelId: "label-id" })
})
```

`card` (ID, short link, or URL) and stable `labelId` are required. Optional `account` defaults to the project binding. Returns the updated `TrelloCard`. The label must belong to the card's board; discover IDs with [List board labels](/reference/integrations/trello/actions/list-board-labels).