[FEATURE] Support for stateless MCP Servers

[stuart-aws]

Problem Statement

One approach to a scalable MCP server architecture is to have multiple stateless server instances (described here). This means there is no persistent session between client and server. Presently when using Streamable HTTP with the MCP Client provided with Strands Agents throws a MCPClientInitializationError whenever it tries to invoke a tool on a stateless server.

Proposed Solution

Allow MCPClient to be created in stateless mode.

Use Case

For use with highly scalable backend MCP Server infrastructure.

Alternatives Solutions

No response

Additional Context

No response

[dbschmigelski]

Hi, thanks for pointing this out! I am going to mark this as a BUG rather than an enhancement. To help us debug can you provide some information about your system: python version, strands version, mcp version, OS, strands installation method, etc?

Can you also show the test code you are using? A common bug related to indentation is often why we see that error message.

[stuart-aws]

Hi @dbschmigelski, thanks for picking this up. I noticed the commit you made yesterday and this did in fact relate to the problem I was experiencing.

I misinterpreted the "the client session is not running" error message as being related to the lack of a persistent session with the Streamable HTTP MCP Server, but it was in fact due to the tool invocation occurring outside of the client context manager.

I have a create_agent function that sets up tools and model config, returning the Agent object. Therefore I've removed the 'with' statement that was used with the MCPClient and I am instead directly calling the start() and stop() functions of the client appropriately.

Thanks for your help, the additional documentation and improved error message. This issue can be closed.

Stuart

[dbschmigelski]

Thanks for the fast reply @stuart-aws, I opened #198 as this seems to be a common problem. I am hoping we can arrive at a less error prone DX through that issue. If you have any thoughts, positive or negative, your input would be appreciated there, thanks!