Its very similar to the switch from a text editor + command line, to having an IDE with a debugger.

the AI gets to do two things:

- expose hidden state - do interactions with the app, and see before/after/errors

it gives more time where the LLM can verify its own work without you needing to step in. Its also a bit more integration test-y than unit.

if you were to add one mcp, make it Playwright or some similar browser automation mcp. Very little has value add over just being able to control a browser