MCP Test MCP

# Bearer Token Authentication > Authenticate your FastMCP client with a Bearer token. export const VersionBadge = ({version}) => { return `<code className="version-badge-container">` `<p className="version-badge">` `<span className="version-badge-label">`New in version:  `<code className="version-badge-version">`{version}`</code>` `</p>` `</code>`; }; <VersionBadge version="2.6.0" /> <Tip> Bearer Token authentication is only relevant for HTTP-based transports. </Tip> You can configure your FastMCP client to use **bearer authentication** by supplying a valid access token. This is most appropriate for service accounts, long-lived API keys, CI/CD, applications where authentication is managed separately, or other non-interactive authentication methods. A Bearer token is a JSON Web Token (JWT) that is used to authenticate a request. It is most commonly used in the `Authorization` header of an HTTP request, using the `Bearer` scheme: ```http Authorization: Bearer <token> ``` ## Client Usage The most straightforward way to use a pre-existing Bearer token is to provide it as a string to the `auth` parameter of the `fastmcp.Client` or transport instance. FastMCP will automatically format it correctly for the `Authorization` header and bearer scheme. <Tip> If you're using a string token, do not include the `Bearer` prefix. FastMCP will add it for you. </Tip> ```python from fastmcp import Client async with Client( "https://fastmcp.cloud/mcp", auth="<your-token>", ) as client: await client.ping() ``` You can also supply a Bearer token to a transport instance, such as `StreamableHttpTransport` or `SSETransport`: ```python from fastmcp import Client from fastmcp.client.transports import StreamableHttpTransport transport = StreamableHttpTransport( "http://fastmcp.cloud/mcp", auth="<your-token>", ) async with Client(transport) as client: await client.ping() ``` ## `BearerAuth` Helper If you prefer to be more explicit and not rely on FastMCP to transform your string token, you can use the `BearerAuth` class yourself, which implements the `httpx.Auth` interface. ```python from fastmcp import Client from fastmcp.client.auth import BearerAuth async with Client( "https://fastmcp.cloud/mcp", auth=BearerAuth(token="<your-token>"), ) as client: await client.ping() ``` ## Custom Headers If the MCP server expects a custom header or token scheme, you can manually set the client's `headers` instead of using the `auth` parameter by setting them on your transport: ```python from fastmcp import Client from fastmcp.client.transports import StreamableHttpTransport async with Client( transport=StreamableHttpTransport( "https://fastmcp.cloud/mcp", headers={"X-API-Key": "<your-token>"}, ), ) as client: await client.ping() ```