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

# Authentication

> Sign in to Flow and authenticate API, CLI, and MCP clients.

Sign in to the web app at [https://app.letsflow.ai](https://app.letsflow.ai).

## Browser sign-in

Use your organization's Flow login. Flow manages session handling after you authenticate.

## Authenticate API and CLI clients

Authenticate API and command-line interface (CLI) clients with API keys or OAuth.

| Method | Typical use |
| - | - |
| API keys | Scripts, service accounts, long-running integrations |
| OAuth | OAuth-protected API surfaces where documented |

<Steps>
  <Step title="Open API and MCP Access.">
    Open **Settings → API & MCP Access**.
  </Step>

  <Step title="Create a key.">
    Create an API key or service account for the integration.
  </Step>

  <Step title="Send the key.">
    Send the key on requests per the [API Reference](/api-reference).
  </Step>
</Steps>

Base URL for machine clients: `https://app.letsflow.ai/v1`.

## Authenticating hosted MCP

Hosted MCP at `https://app.letsflow.ai/mcp` uses OAuth for agent clients. Configure the client per [Hosted MCP](/setup/mcp). API keys are not a substitute for MCP OAuth.

## Authorization

Flow roles and team settings grant capabilities, not directory group membership alone. A valid token or session still requires the capability for the action you call.

## Related topics

* [Day 1 setup](/setup/day-1-setup)
* [CLI](/setup/cli)
* [Hosted MCP](/setup/mcp)
* [API Reference](/api-reference)
* [Settings](/setup/settings)


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