> ## 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.

# On Custom Field value updated

> Run an automation after a Trello card Custom Field value changes.

`trello.onCustomFieldValueUpdated` matches Trello's `updateCustomFieldItem` action for card values.

```ts automations/watch-trello-custom-field-values.automation.ts theme={null}
import { automation } from "automate.ax"
import { trello } from "automate.ax/trello"

export default automation("Watch Trello Custom Field values", () => {
  trello.onCustomFieldValueUpdated({ board: "board-id" })
})
```

Provide `board` as an ID, short link, or URL. Optional static `account` defaults to the project binding.

Returns a resource event with `actionType: "updateCustomFieldItem"`, required `card`, `customField`, `customFieldItem`, and `board`, plus `actionId`, `occurredAt`, optional `old` and `memberCreator`, and the complete provider `event`.