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

# Output & exit codes

> JSON on stdout, a structured error object on stderr, and stable exit codes an agent can branch on.

The CLI is built to be driven by scripts and AI agents, so its output contract
is deterministic and machine-readable.

## Output

* **Success**: JSON on stdout — indented by default (readable), compact
  single-line with `--json` (for pipes and `jq`).
* **Failure**: a structured error object on stderr, shaped
  `{ "error", "message", "status", "details" }`. HTTP errors carry an
  actionable message for `400`, `401`, `403`, `404` and `429`.

```bash theme={"theme":"dracula"}
lemlist --json campaigns list | jq '.[0].name'
```

<Note>
  `lemlist endpoints` prints a text table by default, and a JSON array under
  `--json`. A richer human-readable table for endpoint responses is a future
  refinement — today the default is indented JSON.
</Note>

## Exit codes

Every run ends with an exit code that signals the failure class, so an agent
or script can branch without parsing stderr:

| Code | Meaning                                                     |
| ---- | ----------------------------------------------------------- |
| `0`  | Success                                                     |
| `1`  | Validation error (bad arguments or malformed `--data` JSON) |
| `2`  | Authentication error (missing or invalid credential)        |
| `3`  | Rate limit                                                  |
| `4`  | Network error or timeout                                    |
| `5`  | Not found (unknown endpoint or missing resource)            |
| `6`  | Unknown error                                               |

## Automatic retries

Transient failures — network errors, `5xx` responses and `429` rate limits —
are retried automatically with exponential backoff (a `Retry-After` header is
honored).

<Warning>
  Retries are safe by design: a `429` means the server rejected the request, so
  it is always replayed. A `5xx` or a network drop may land **after** a write was
  processed, so only idempotent methods (`GET`, `PUT`, `DELETE`) are replayed in
  that case — a `POST` or `PATCH` is never retried on those failures, to avoid
  double-creating a resource.
</Warning>

## Unknown endpoints

When a path is missing from the OpenAPI spec, `lemlist api` returns
`UNKNOWN_ENDPOINT` (exit code `5`) with the closest matching endpoints:

```json theme={"theme":"dracula"}
{
  "error": "UNKNOWN_ENDPOINT",
  "message": "No GET /campaign in the OpenAPI spec.",
  "suggestions": ["GET /campaigns", "GET /campaigns/{campaignId}"]
}
```

Run `lemlist endpoints --refresh` if you expect a newly deployed endpoint that
the cached spec does not yet know about.

***

[give us feedback on this page](https://lemlist.typeform.com/to/mfVlkyGf)