The tools find the problem. The product fixes it.
A break you had to find by pasting CSVs into a web page is a break nothing was watching for. Test mode is free, takes no card, and runs the same engine as live.
Free tools
Paste a processor export and your own balances. It reports the breaks that did not match, in your numbers, in your browser.
Payments and finance engineers · A drift report
Answer four questions about what an agent may spend and get a valid policy plus the call to test it against.
Teams putting agents in production · Policy JSON and a curl
What building your own double-entry ledger costs in engineering months, itemised, with every assumption on screen.
Engineering leads deciding build or buy · An estimate you can argue with
Each one runs client-side. You can open the network tab and watch nothing get sent, or disconnect and use them offline.