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

# Authentication

> Obtain a PolyAI API key and configure your MCP client to authenticate against the Builder MCP.

PolyAI's MCP servers authenticate with the same [workspace-scoped API key](/secrets/api-keys) used across PolyAI's APIs, sent in the `X-API-KEY` header.

## Get an API key

<Steps>
  <Step title="Open the API Keys page">
    Go to the **API Keys** tab on your workspace homepage in Agent Studio. See [API keys](/secrets/api-keys) for details.
  </Step>

  <Step title="Create a key">
    Select **API key**, name it, choose the agents it can access, and set its permissions. Scope it to the least it needs — see [Security & safe use](/mcp/builder/security#use-least-privilege-keys).
  </Step>

  <Step title="Copy the value">
    The full key is shown only once. Copy it immediately and store it in your client's secret settings — never paste it into a chat prompt.
  </Step>
</Steps>

<Frame caption="The API Keys tab on your workspace homepage in Agent Studio.">
  <img src="https://mintcdn.com/polyai/XrMtC1rV8-sgJgHo/images/secrets/api-keys-overview.png?fit=max&auto=format&n=XrMtC1rV8-sgJgHo&q=85&s=6274a720218a02525d85365d20600256" alt="The API Keys tab in Agent Studio, showing the list of keys and the 'API key' button to create a new one" style={{ maxWidth: '820px', width: '100%', margin: '0 auto', display: 'block' }} width="2358" height="1388" data-path="images/secrets/api-keys-overview.png" />
</Frame>

## Configure your client

Pass the key in the `X-API-KEY` header. The MCP server uses the streamable HTTP transport, so clients also send an `Accept` header:

| Header      | Value                                 |
| ----------- | ------------------------------------- |
| `X-API-KEY` | Your workspace-scoped API key         |
| `Accept`    | `application/json, text/event-stream` |

Most clients set `Accept` automatically. See [Quickstart](/mcp/quickstart#2-add-the-server-to-your-client) for per-client configuration.

## Pick your region

PolyAI runs the MCP server in every region, on the same host family as the [platform APIs](/api-reference/introduction#pick-your-region). Your API key is scoped to a workspace, and each workspace lives in one region — connect to the matching endpoint.

| Region | Endpoint                                 |
| ------ | ---------------------------------------- |
| US     | `https://api.us.poly.ai/builder-mcp`     |
| UK     | `https://api.uk.poly.ai/builder-mcp`     |
| EU     | `https://api.eu.poly.ai/builder-mcp`     |
| Studio | `https://api.studio.poly.ai/builder-mcp` |

## OAuth (coming soon)

Browser-based OAuth is on the roadmap — you'll be able to authorize a client without manually creating and pasting a key. **At launch, use API-key authentication as described above.** This page will cover OAuth once it ships.