# tags.merge

Merge one project tag into another with sourceId, targetId, the source's expectedRevision and idempotencyKey: every transaction tagged with the source gets the target instead (once), learned rules and the tags inside a merged group move too, and the source is archived. The audit records every transaction moved.

`POST /api/v1/accounting/tags.merge`

Permissions: `accounting:read`, `accounting:write` · Roles: admin, finance · Idempotency key required · Send `expectedRevision`

MCP tool: `accounting_tags_merge`

## Fields

| Field | Type | Required | Notes |
| --- | --- | --- | --- |
| `sourceId` | string (ID) | Yes | The ID of the related record. |
| `targetId` | string (ID) | Yes | The ID of the related record. |
| `expectedRevision` | integer | Yes | The record's current revision, from the last time you read it. If someone changed the record since, the request is refused with a conflict so you can reload and check before trying again. at most 9007199254740991; greater than 0. |
| `idempotencyKey` | string | Yes | Any unique text you generate once per intended change, so a retried request only happens once. Send it as the Idempotency-Key header instead if you prefer; if you send both they must match. 8–200 characters. |

## Example request

```bash
curl https://app.getoatmilk.com/api/v1/accounting/tags.merge \
  -H "Authorization: Bearer $OATMILK_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d '{
  "sourceId": "1a2b3c4d-5e6f-4a7b-8c9d-0e1f2a3b4c5d",
  "targetId": "4d5e6f7a-8b9c-4d0e-8f1a-2b3c4d5e6f7a",
  "expectedRevision": 3
}'
```

Reference page: https://app.getoatmilk.com/docs/api/tags.merge