ensure only available server capabilities are fetched

[mollux]

Context

Currently the possible tools, resources and resources templates are fetched in the McpHub.connectToServer method.

Based on the spec, during Initialization phase, the capabilities of both client and server must be negotiated.

So it would make sense to ensure that e.g. resources are not fetched (or give an error while trying to fetch them) if the server already defined it doesn't support them.

If Pr addresses this

(see also #3350)

Implementation

• added a helper method McpHub:fetchAvailableServerCapabilities that checks the server capabilities before fetching hem
• added a check in all existing fetch...List methods to verify if the server capability is supported.

Depending on the approach, the check could also only live in the fetch...List methods, and McpHub:fetchAvailableServerCapabilities only be used as an easy helper method to fetch all capabilities, as there are others too.

Screenshots

before	after

How to Test

• use an MCP server that doesn't support tools or resources
• verify that there are no calls (and thus errors) for fetching those capabilities

Get in Touch

Discord handle: mollux
GitLab profile: https://gitlab.com/mmichaux-ext

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