Give subagents access to more tools than the main agent

When using the SDK, I want to specialize a given subagent by giving it access to tools that I don't want to give the main agent.

Example:
I don't want the main agent to get its context dirty with grepping code and searching logs. I have subagents for that, but since (for example) the main agent have access to the code (on disk) and the logs (via MCP), it sometimes tries to investigate directly.

What I want:
main agent tools: [X, Y]
subagent tools: [X, Z]

However, the main agent doesn't have access to Z -- so te subagent won't get it either.