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

# Introduction

> Learn how the UseAgents API is structured, how to authenticate requests, and where to start with the available endpoints.

The UseAgents API lets you search the tool registry and build integrations around UseAgents data. Start here to understand the base URL, authentication model, response behavior, and supporting reference pages.

## Base URL

The UseAgents API is HTTPS-only and follows standard REST patterns.

All requests use the following base URL:

```text theme={null}
https://api.useagents.site
```

<Note>
  The UseAgents API is **currently free** during our public beta. No API key is required. Requests are subject to [rate limits](/api-reference/rate-limit) to ensure reliability.
</Note>

## Authentication

Protected endpoints require an `Authorization` header with your API key as a Bearer token.

```text theme={null}
Authorization: Bearer YOUR_API_KEY
```

Learn more about [Authentication](/api-reference/authentication).

## Response codes

UseAgents uses standard HTTP status codes. In general:

* `2xx` means the request succeeded
* `4xx` means the request was invalid, unauthorized, or rate limited
* `5xx` means the request failed due to a server-side issue

| Status | Description                                          |
| ------ | ---------------------------------------------------- |
| `200`  | Successful request.                                  |
| `400`  | Bad request. Check that the parameters were correct. |
| `401`  | The API key was missing.                             |
| `403`  | The API key was invalid.                             |
| `404`  | The resource was not found.                          |
| `422`  | Validation error with one or more fields.            |
| `429`  | The rate limit was exceeded.                         |
| `5xx`  | Indicates an error with UseAgents servers.           |

<Info>
  Check [Errors](/api-reference/errors) for a full breakdown of common failure
  cases.
</Info>

## Rate limits

Authenticated endpoints are rate limited to protect service stability and ensure fair usage. If you exceed the allowed rate, the API returns `429 Too Many Requests`.

Learn more on the [Rate Limits](/api-reference/rate-limit) page.

## Versioning

UseAgents aims to keep existing integrations stable as the API evolves.

Learn more on the [Versioning](/api-reference/versioning) page.

## Next steps

* [Authentication](/api-reference/authentication) to add the correct headers
* [Tools Search](/api-reference/tools-search) for the main search endpoint
* [Errors](/api-reference/errors) to troubleshoot failed requests