Keys & data
Add an API key so the tools can run prompts on real AI models, see exactly what each key has been used for, and export or delete everything this browser keeps.
What is an API key, and why do I need one?
An AI model like Claude, GPT or Gemini runs on its maker's computers. An API key is a long password-like code from that company that lets a program, such as these tools, send prompts to the model on your account. Each request is billed to you by the company that runs the model, usually a fraction of a cent.
thinkhard.si asks for your key instead of using its own, so you pay the provider directly at their list price with nothing added, you choose which models to use, and your prompts go straight from this browser to the provider without passing through us.
You can start for free. Google AI Studio, OpenRouter and Groq give free keys with free models. Several tools need no key at all: the Grader's instant estimate, the cost calculator, Version Compare, My Prompts and the templates.
Read the full guide to API keys See what your keys were used for
What each tool uses a key for
- Prompt Grader
- Three short calls each time you improve a prompt with AI: a review, a rewrite and a check. Two more and a judge if you test both versions. The score and the questions need no key.
- Prompt Tester
- One call per test case, per version, per model, plus one judge call per answer when the AI judge is on. The Run tab shows the count and an estimate before you start.
- Model Compare
- One call per model you pick, plus one for the judge if you ask for it.
- Chatbot Safety Test
- One call per attack probe, per model, plus a judge call when a reply is unclear. The scan needs no key.
- Cost calculator
- Only for exact token counts with an Anthropic or Google key. Those requests count words and write nothing.
- Version Compare, My Prompts, Templates
- Never.
What a typical run costs
API keys
Add at least one. No key yet? Google AI Studio, OpenRouter and Groq give free keys that work here.
What your keys were used for
Every model call made from this browser, newest first: when, which tool, which model, how much text went each way and an estimated cost. Your prompts and answers are not stored here, and this log never leaves your browser. Your provider's bill is the final word on cost.
Default models
Used when a tool needs a model and you have not picked one: the fast model grades and judges, the capable model rewrites.
Your data
Saved prompts, test suites and results live in this browser only. Export them to move to another device; keys are never exported.
How your keys are handled
- Keys are kept in this browser's storage. Turn off Remember to keep a key only until you close the tab.
- Each key is sent only to its own provider, over HTTPS, straight from your browser. thinkhard.si has no server that sees it.
- The site loads no third-party trackers or ads, and a strict content security policy limits which scripts can run.
- Put a spending limit or a small prepaid balance on every key you use in a browser. Most providers offer one or the other in their billing settings.