this is how i've been solving the problem before some of these newer techniques around deferred loading etc. came out

a subagent per mcp toolset, basically sub agent per saas in the configuration at $WORK

I don't have any hard evals on this but it feels like it works more than it doesn't, especially now that subagent use has gotten better in general, but you do feel drawbacks if you ever need to do something that involves coordinating multiple sub agents, there's some communication overhead that wouldn't be there if it was just one agent with all the tools to do the whole job