# POST /api/v2/work-items/{work_item}/subtasks

Add a subtask to a work item

- MCP id: work-items.subtasks.store
- Scope: api:write:project_management
- Permission: project_management::manage_work_items
- Rate cost: 1 unit, write bucket. A write costs the same whatever `view` you ask for.
- Cache-Control: private, no-store

Creates one checklist subtask on the work item named in the path and returns it in the detail view, with a `Location` header pointing at the flat item path.

The work item comes from the path, so `work_item_id` is not accepted in the body and a subtask can never be moved between work items. The new subtask is appended to the end of that work item's checklist; `order` is not accepted, and reordering is not available through the API. There is no batch create: post one subtask per request.

## Parameters
- work_item (integer or string, path): The WorkItem's numeric id. Or its issue_key, matching `[A-Z][A-Z0-9]*-[0-9]+`.
- view (string, optional): Which field set to render.
- X-Request-Id (header, optional): A correlation id of your own. It is recorded in our logs next to the server's request id but never returned: the response header always carries the server's id. A value that does not match the pattern is discarded silently, never rejected.
- Idempotency-Key (header, optional): A caller-chosen key that makes this POST safe to retry. Replaying it returns the original response with Idempotency-Replayed: true.

## Request body
- title (string ≤ 255, required): Subtask title, as shown on the checklist row. This is the field `?q=` searches.
- description (string or null, optional): Optional note on the subtask. HTML from the rich editor, sanitised on read and on write. Null when the subtask is just a title.
- is_resolved (boolean, optional): Whether the subtask is ticked off.

Unknown keys are refused with `422` validation-failed, naming the key.

## Response 201
- id (integer, required): Unique identifier.
- work_item_id (integer, required, server-assigned): The work item whose checklist this subtask belongs to. Taken from the path on create and not writable.
- title (string ≤ 255, required): Subtask title, as shown on the checklist row. This is the field `?q=` searches.
- description (html or null, required, detail only): Optional note on the subtask. HTML from the rich editor, sanitised on read and on write. Null when the subtask is just a title.
- is_resolved (boolean, required): Whether the subtask is ticked off.
- order (integer, required, server-assigned): Position in the work item's checklist. Assigned on create as the next position in that checklist, changed only by dragging in plnnrly, and not writable.
- created_at (timestamp (YYYY-MM-DDThh:mm:ssZ), required): Creation timestamp.
- updated_at (timestamp (YYYY-MM-DDThh:mm:ssZ), required): Last-write timestamp; use for incremental sync.
- work_item (Ref or WorkItemSummary, required): The work item this subtask hangs off.
- links (SubtaskLinks, required)
  - self (url, required): The canonical URI of this record.

## Errors
- 403 forbidden-by-policy | insufficient-permission | insufficient-token-scope: Forbidden.
- 409 idempotency-key-in-flight | idempotency-key-reused: Conflict.
- 415 unsupported-media-type: Unsupported media type.
- 422 unprocessable-relationship | validation-failed: Unprocessable content.
- 400 idempotency-key-required | invalid-cursor | invalid-query-parameter | malformed-request | unsupported-parameter: Bad request.
- 401 token-expired | unauthenticated: Unauthenticated.
- 404 endpoint-not-found | resource-not-found: Not found.
- 406 not-acceptable: Not acceptable.
- 429 rate-limit-exceeded: Too many requests.
- 500 internal-error: Server error.
- 503 tenant-unavailable: Service unavailable.

## Example
```bash
curl -X POST \
  'https://<your-url>/api/v2/work-items/1/subtasks' \
  -H 'Authorization: Bearer <token>' \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  -H 'Idempotency-Key: <key>' \
  -d '{
    "title": "Wire up the SSO callback"
  }'
```