Why do we need broadcast messages to clients？

[JadenHuang2023]

java-sdk/mcp-spring/mcp-spring-webflux/src/main/java/io/modelcontextprotocol/server/transport/WebFluxSseServerTransport.java

Line 189 in 352ec2d

logger.debug("Attempting to broadcast message to {} active sessions", sessions.size());

Why do we broadcast responses to all clients instead of just sending them to the current requesting client?

[tzolov]

@JadenHuang2023, Thanks for the relevant question.
Some server notifications (tools/resource/prompt list changes) should be broadcast to all clients, while server requests related to Roots and Sampling should only go to the initiating client's session. Later is not implemented correctly at the moment. We'll fix this behavior soon.

[JadenHuang2023]

@tzolov Thanks for your response.
The result of the tool call/tool list, etc should also only be sent to the current requesting client.

[taobaorun]

https://stackoverflow.com/questions/79456135/java-mcp-sdk-webflux-server-transport-sendmessage-is-broadcasts

The current version of the tool call is also broadcast to all clients。

[marianogonzalez]

@tzolov will the behavior fix you're describing include avoiding broadcast for tool/call or resource/read responses? Do you happen to have an ETA on that fix? Thanks!

[tzolov]

@taobaorun, @marianogonzalez we're developing a proper client session management solution that will address all issues mentioned above, including handling for listRoots and createMessage (sampling).

Some early experiments are available at https://github.com/modelcontextprotocol/java-sdk/tree/server-session-support2, and we expect to finalize the solution soon.