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

# Authentication

> Authenticate with the Instantly MCP server using headers or URL paths.

The Instantly MCP server supports multiple authentication methods. Choose the one that fits your MCP client.

## Header authentication

Send your API key in the `Authorization` header. This is the recommended method — it keeps your key out of server access logs and client history.

```
URL: https://mcp.instantly.ai/mcp
Header: Authorization: YOUR_API_KEY
```

The bearer token prefix is also accepted:

```
URL: https://mcp.instantly.ai/mcp
Header: Authorization: Bearer YOUR_API_KEY
```

## Custom header

Use the `x-instantly-api-key` header if your client does not support the `Authorization` header.

```
URL: https://mcp.instantly.ai/mcp
Header: x-instantly-api-key: YOUR_API_KEY
```

## URL-based authentication

Use this only if your MCP client cannot set custom headers. The key is part of the request URL, so it may be recorded in intermediary and server logs.

```
https://mcp.instantly.ai/mcp/YOUR_API_KEY
```

<Warning>
  Keep your API key secure. Never expose it in client-side code, share configuration files that contain it, or commit it to source control.
</Warning>