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

# Introduction

> Learn about Relace API organization, general response codes, and authentication strategies.

## Base URLs

The Relace API is organized into two distinct domain patterns: `*.endpoint.relace.run` domains for direct AI model access, and `api.relace.run` for general infrastructure services including source control.

### Model Endpoints

```
https://*.endpoint.relace.run
```

To use our hosted models the url pattern follows the above convention -- the \* is a placeholder for the series of model you are using. *e.g.* `instantapply`, `ranker`, `embeddings`.

### Infrastructure Endpoints

```
https://api.relace.run
```

For accessing our infrastructure (*e.g.* source control) you will use the routes specified in this API reference with our common base url.

## Authentication

To authenticate you need to add an Authorization header with the contents of the header being your Relace API Key, which is a 32 digit key with with the prefix `rlc-`.

```
Authorization: Bearer rlc-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
```

## Response Codes

Relace uses standard HTTP codes to indicate the success or failure of your requests.

In general, 2xx HTTP codes correspond to success, 4xx codes are for user-related failures, and 5xx codes are for infrastructure issues.

| Status               | Description                                        |
| -------------------- | -------------------------------------------------- |
| <small>`200`</small> | Successful request.                                |
| <small>`201`</small> | Resource created successfully.                     |
| <small>`204`</small> | Successful request, no content returned.           |
| <small>`400`</small> | Check that the parameters were correct.            |
| <small>`401`</small> | The API key used was missing or invalid.           |
| <small>`403`</small> | The API key used was invalid or lacks permissions. |
| <small>`404`</small> | The resource was not found.                        |
| <small>`423`</small> | The resource is temporarily locked.                |
| <small>`429`</small> | The rate limit was exceeded.                       |
| <small>`5xx`</small> | Indicates an error with Relace servers.            |

Check [Error Codes](/api-reference/errors) for a comprehensive breakdown of all possible API errors.

## Rate Limits

Rate limits vary by tier and range from 3 calls per minute for free testing access to unlimited calls for high-volume users. When you exceed your rate limit, you'll receive a 429 response error code.

See the full [rate limits table](/docs/policies#rate-limits) for detailed information about each tier's limits.