From my understanding there is no solid documentation yet as the API is still in development.
However, it’s a REST API and you can see what’s available by signing up for a trial on the Cloud edition and visiting the /api route in your web browser of choice. You can access the API before paying.
This is the route you would visit: https://subdomain.manager.io/api
Password: As entered when signing up
As long as you have created a business (you can use the sample business Northwind - Sample Business if you wish), you will be able to navigate through the data that is accessible via the API.
It’s actually very self-explanatory / almost serves as documentation by itself, but feel free to reply here if you have any questions about it.
You sound like you have the same requirements as I do, and that’s what led me to Manager!
System I created integrates Manager, Bank account statements and our ERP, but there is one very annoying issue. We can not create Receipt with API with preselected Invoice just because we can not QUERY invoices either for particular Customer, not by any other field including Invoice ID. The only way to query invoices is to fetch all of them (more than 2000 in our case) and then to mock/cache locally with kind of DB.
And this really makes me upset. Is there any chance to increase importance of this feature?