I am not sure why...you want the LLM to solve problems not come up with answers itself. It's allowed to use tools, precisely because it tends to make stuff up. In general, only if you're benchmarking LLMs you care about whether the LLM itself provided the answer or it used a tool. If you ask it to convert the notation of sheet music it might use a tool, and it's probably the right decision.
The shortcut is fine if it's a bog standard canonical arrangement of the piece. If it's a custom jazz rendition you composed with an odd key changes and and shifting time signatures, taking that shortcut is not going to yield the intended result. It's choosing the wrong tool to help which makes it unreliable for this task.
