What should you check before offering furniture assembly?
Think about the furniture you've built, which steps you did yourself and where you needed help. A small table at home doesn't prepare you for every wardrobe. The model and manufacturer's instructions give you more to discuss than a broad handyman label.
Ask what is waiting in the box. Are all the parts there, has someone started assembling it, and what do they expect at the end? Carrying boxes, removing packaging and fixing furniture to a wall need separate agreement. An extra line in a message shouldn't silently add to what you agreed to do.
When does assembly need installation expertise?
Read the guide to getting started with furniture assembly to describe your experience and ask about the model. It also explains the difference between building a freestanding unit and attaching a shelf to a wall. Both may involve screws, but they need different knowledge.
Electrical work, gas, plumbing, work at height and specialist repairs are outside this guide and need an appropriate professional. If the manufacturer requires securing the piece, or another step you can't do, the furniture isn't ready for use. Find out who can complete that step rather than skipping it.