Get your OpenRouter key
Takes about 2 minutes. You'll need a credit card for ~$1 in credits to get started — you'll top up to $20 in step 2.
Faster option: on the main form you can click “Log in with OpenRouter” to authorize coarse and skip manual key creation. You still need an OpenRouter account with credits (steps 1 and 2 below), and we still recommend setting a per-key spend limit (step 4).
Create an account
Go to openrouter.ai and click “Get API Key” or sign up with Google / GitHub.
Add credits
Navigate to Settings → Credits. Add at least $20. Cheap open-source models cost ~$0.25 per review; SOTA models like Claude Opus or GPT-5 can run $5–$10 on a long paper. The cost estimate shown before submission is a ballpark, not a ceiling. Leave headroom or the review can exhaust the key halfway and fail. Unused credits don't expire.
Create an API key
Go to Settings → Keys, click “Create Key”, and name it coarse.
Make sure it's a regular API key — not a provisioning/management key from the integrations section. Provisioning keys can create and list other keys but can't run inference, and coarse will fail with “User not found” if you paste one.
Copy the key now — you won't see it again.
Set a spending limit on the key
On the Keys page, click the ⋮ menu next to your new key, choose “Edit”, and set the credit limit to at least $20. The key stops working once the limit is hit, so surprise charges are impossible. But set it too tight and a single expensive review can exhaust it mid-run.
Why this matters: coarse is open-source — you can read every line of code. Your key is sent directly to OpenRouter to run the review, then discarded — it is never stored. But you don't have to trust us: the per-key limit guarantees it can never spend more than you allow, even in the worst case.
A note on cost estimates: the estimate shown before submission is a heuristic with a ~15% buffer, not a hard ceiling. Actual cost on SOTA models with long papers can run up to ~2× the estimate once proof-verification and critique rewrites kick in. If the per-key cap sits right at the estimate, one tough review can drain it and fail mid-run. Always leave headroom.
Paste into coarse
Come back here, paste your key into the form, and upload your PDF.