The other comment already mentioned that you get their subscription: https://mistral.ai/pricing/ they do say that you can try out their coding agent for free, but personally the Pro tier is pretty affordable too to try out for a month.

Then you can install their coding harness, I personally used the Python + uv option: https://mistral.ai/products/vibe/code/ if you don't have uv yet, you might have to install it too: https://docs.astral.sh/uv/ though I already use it for other projects. Oh and if on Windows, you probably want to do all of the installation inside of WSL, just so that file paths are the *nix variety, I've had issues otherwise with pretty much every coding harness, like OpenCode as well (across multiple models).

After that, you need an API key for your subscription, you can generate and copy it here: https://console.mistral.ai/codestral/cli that's also where you see the quota, though it seems to NOT refresh instantly, but more or less a few times a day.

Either way, happy coding!