Resource subscription in MCP Inspector

[cliffhall]

Pre-submission Checklist

• I have verified this would not be more appropriate as a feature request in a specific repository
• I have searched existing discussions to avoid duplicates

Your Idea

Feature Request

Add functionality to MCP Inspector for subscribing to a resource.

Exposing a Dynamic Resource

I have an SSE-based MCP that exposes a dynamic resource - finite state machines (called puzzles).

From the MCP Inspector, I can list the resources, and I can use the resource template to enter a puzzleId and get a snapshot of the puzzle. So far so good.

Subscribing to Changes

I want to allow clients to subscribe to to a given puzzle so that they can be updated with a server-sent event when its state changes.

Server-side

Examples are clear.

• The mcp-servers/everythingexample shows how to accept subscribe and unsubscribe requests.
• It simulates changes happening and being reported with a setInterval that sends notifications for all the dummy resources ever so often.

Client-side

There is no affordance in the the reference client - the MCP Inspector - for subscribing to a resource.

When a resource is selected, there is a refresh button. It seems like an obvious place for a companion toggle button: Subscribe | Unsubscribe. It would send a subscribe or unsubscribe request to the server.

Scope

• Protocol Specification
• SDK Features
• Documentation
• Developer Experience
• Other

[olaservo]

Hi @cliffhall I copied this as a feature request issue to the inspector repo for a little more visibility when people are looking for issues to pick for for inspector: modelcontextprotocol/inspector#166

[cliffhall]

Thanks, @olaservo I'm going to have a look at it. The inspector seems quite complete, except for this bit. I suspect there might be a gotcha involved because of the proxy server connection the inspector uses.