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88 lines
2.7 KiB
Text
88 lines
2.7 KiB
Text
---
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title: Bearer Token Authentication
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sidebarTitle: Bearer Auth
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description: Authenticate your FastMCP client with a Bearer token.
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icon: key
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---
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import { VersionBadge } from "/snippets/version-badge.mdx"
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<VersionBadge version="2.6.0" />
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<Tip>
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Bearer Token authentication is only relevant for HTTP-based transports.
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</Tip>
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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.
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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:
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```http
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Authorization: Bearer <token>
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```
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## Client Usage
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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.
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<Tip>
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If you're using a string token, do not include the `Bearer` prefix. FastMCP will add it for you.
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</Tip>
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```python {5}
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from fastmcp import Client
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async with Client(
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"https://your-server.fastmcp.app/mcp",
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auth="<your-token>",
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) as client:
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await client.ping()
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```
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You can also supply a Bearer token to a transport instance, such as `StreamableHttpTransport` or `SSETransport`:
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```python {6}
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from fastmcp import Client
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from fastmcp.client.transports import StreamableHttpTransport
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transport = StreamableHttpTransport(
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"http://your-server.fastmcp.app/mcp",
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auth="<your-token>",
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)
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async with Client(transport) as client:
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await client.ping()
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```
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## `BearerAuth` Helper
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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.
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```python {6}
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from fastmcp import Client
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from fastmcp.client.auth import BearerAuth
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async with Client(
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"https://your-server.fastmcp.app/mcp",
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auth=BearerAuth(token="<your-token>"),
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) as client:
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await client.ping()
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```
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## Custom Headers
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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:
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```python {5}
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from fastmcp import Client
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from fastmcp.client.transports import StreamableHttpTransport
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async with Client(
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transport=StreamableHttpTransport(
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"https://your-server.fastmcp.app/mcp",
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headers={"X-API-Key": "<your-token>"},
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),
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) as client:
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await client.ping()
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```
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