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

# not_implemented

> 501 api_error — the route is documented and planned, but not yet served. Not a permissions or ownership problem.

**HTTP 501 · type `api_error`.** The route you called is part of the published
contract but has not shipped yet — it is marked `x-fn-status: planned` in the
[API reference](/api-reference). Nothing about your account, key, or resource is
wrong; the surface simply isn't live. Retrying won't help; the
[changelog](/changelog) announces when planned surfaces ship.

## The shape

```json theme={null}
{
  "error": {
    "type": "api_error",
    "code": "not_implemented",
    "message": "POST /v1/discover is not yet available — it is a planned surface.",
    "doc_url": "https://docs.fiveninelabs.com/errors/not_implemented",
    "request_id": "req_c0e73c"
  }
}
```

<Warning>
  **Distinguishing "not shipped" from "wrong id":** planned routes answer **`501
    not_implemented`** with the `surface` named in the error, while a genuinely unknown
  resource answers `404 not_found`. If you see a 501, the route is marked
  `x-fn-status: planned` in the reference and simply has not shipped yet — your account
  is not missing a feature flag. The planned surfaces today: discover, extractions (single and batch),
  monitors, session/extraction refresh, redaction (`DELETE`), `GET /v1/receipts/{id}`,
  webhook test deliveries and redelivery, and `/mcp`.
</Warning>

## How to fix

* Check the [API reference](/api-reference) — if the operation is marked
  `x-fn-status: planned`, build against the live surface instead (sessions cover
  most workflows today) and watch the [changelog](/changelog).
* If the route is **not** marked planned and you get this (or a 404 you can't
  explain), check the HTTP verb — a wrong method on a known path currently returns
  404 as well — then include `request_id` in a support message.