A team is adding stock lookups to a Claude assistant. The stock figures come from an internal REST service that is reachable only from inside the company network and requires a credential the company issues. An engineer proposes enabling one of the server-side built-in tools that Anthropic executes on its own infrastructure, arguing that this avoids writing any handler code. Which assessment of that proposal is correct?
- AThe proposal works once the team supplies the service credential alongside the built-in tool definition, because the built-in tool then presents that credential when it reaches the internal stock endpoint.
- BThe proposal fails, because built-in tools cannot be combined with custom tools in one request; the team must move every existing custom tool onto a server-side definition before stock lookups can work.
- CThe proposal fails, because a server-side built-in tool runs on Anthropic's infrastructure and cannot reach a private endpoint; declare a custom tool whose handler the team's own code executes inside the network. Correct
- DThe proposal works, because the assistant will describe the stock query in its request and the team's integration layer can intercept the built-in tool call and answer it from the internal service instead.
Why A is wrong: Tempting because attaching a credential is how most integrations gain access, but a credential does not create network reachability and the built-in tools do not accept an arbitrary internal endpoint as a target.
Why B is wrong: Tempting because it correctly rejects the proposal, but the stated reason is wrong: the two kinds of tool coexist in a request, and the real obstacle is where the tool executes.
Why C is correct: Correct: where the tool executes decides what it can reach, and only a client-side custom tool runs inside the network boundary where the stock service and its credential live.
Why D is wrong: Tempting because interception sounds like a thin shim, but a server-side tool is executed by the provider and never surfaces to the client as a call to answer, so there is nothing for the integration to intercept.