---
title: fields.define | Doing Work API
description: Add a custom field to customers, properties, jobs, quotes or invoices for a shop.
url: https://doingwork.work/docs/reference/fields-define/
---

# fields.define

Add a custom field to customers, properties, jobs, quotes or invoices for a shop.

|  |  |
|---|---|
| Who | Agents can call this |
| REST | `POST /v1/fields` |
| MCP tool | `fields_define` |
| Writes | yes, send an Idempotency-Key |
| Area | [Imports, custom fields, tags and search](https://doingwork.work/docs/reference/#imports-custom-fields-tags-and-search) |

## When to use it

Add a custom field to customers, properties, jobs, quotes or invoices for a shop.

## What to tell the owner

Say what you did in plain words and what happens next.

## Input

| Field | Type | Required |
|---|---|---|
| `shop_id` | string (uuid) | yes |
| `key` | string | yes |
| `label` | string | no |
| `target` | string (one of customer, property, job, quote, invoice) | yes |
| `type` | string (one of text, number, money, date, boolean, enum, json) | yes |
| `options` | array | no |
| `required` | boolean | no |
| `pii` | boolean | no |
| `shared_with_homeowner` | boolean | no |

## Example

```http
POST https://doingwork.work/v1/fields
content-type: application/json
Idempotency-Key: 3f1c...

{
  "shop_id": "00000000-0000-4000-8000-000000000000",
  "key": "...",
  "target": "customer",
  "type": "text"
}
```

## Output

JSON. The response shape isn't published yet; read the fields you need and ignore the rest. Errors are `{code, message, status}`.

## Errors

| Code | Status | What to do |
|---|---|---|
| `invalid_input`, `invalid_token`, `rate_limited` |  | Can happen on any call. See [errors](https://doingwork.work/docs/errors/). |