MCP Tools: No mechanism to pass user JWT token through ADK session.state to MCP server context

[pandasanjay]

Description

Scenario

• Our MCP Tools are intended for internal use and rely on API calls that require a user JWT token for authentication.
• The ADK session.state can hold the JWT token, but the current implementation of MCP tools does not have direct access to the Context.
• Even if some context access is possible, there is no mechanism to propagate the JWT token from the ADK session to the MCP server context.

Impact

• MCP Tools cannot authenticate API requests on behalf of the user, blocking essential functionality.
• There is a gap between where the JWT token resides (ADK session.state) and where it is needed (MCP server context).

Text-Based Flow Diagram

+----------+     +--------------------------+     +-------------+     +--------------------+     +-------------+
|   User   | --> | ADK Session              | --> |  MCP Tool   | -X->| MCP Server Context | --> | Backend API |
+----------+     | (JWT Token Stored Here)  |     |             |     | (Needs JWT Token)  |     | (Needs JWT) |
                   +--------------------------+     +-------------+     +--------------------+     +-------------+
                                                            |
                                                            |
                                                            V
                                                      Problem Area:
                                                      MCP Tool cannot pass JWT
                                                      from ADK Session to
                                                      MCP Server Context.
                                                      The "-X->" indicates the broken path.

Where Things Fall Apart

• The MCP Tool does not have a mechanism to retrieve the JWT token from the ADK Session.
• Consequently, there is no way to provide this JWT token to the MCP Server Context, which needs it to make authenticated calls to the Backend API.

Proposed solution - #1198

[Jacksunwei]

@seanzhou1023 is this something that you're working on?

[pandasanjay]

Just few more context where and why we need it:

I’m developing a multi-user MAS where agents can autonomously schedule background tasks on behalf of users. To ensure secure access and prevent unauthorized usage of user resources, I’m implementing JWT tokens in the sessions at the user state level. This ensures that user identities and their conversation sessions are isolated and not confused with others.

The approach works seamlessly with ADK tools using CallbackContext or ToolContext. However, it doesn’t function as expected when applied to MCP as this information needed passed to MCP STDIO session to used as Env variable.

But for other MCP transports like Streamable HTTP,need to explore some way to pass this existing token, instead of re authenticating.

[muliu]

I also have such a requestment.

The MCP Server used by the Agent requires authentication (check the Authorization Token in the HTTP header sent to the MCP Server)

Assuming I already have a Token, the question now is: In ADK, what method should I use to transfer the Token to MCP Server?