Reminds me a of a short lived project websocket.email. Instead of webhook, you could listen on websocket for emails. Might be a Pro feature for your project.
I had this idea to basically have the Budgeting app look at the notifications on my phone or emails from the bank to parse the transactions details automatically.
On iOS if an app exposes a Shortcut, I could setup a Shortcut Automation to automatically add an expense when a new email from my bank shows up. Would need some REGEX or LLM ;)
`XOR[0...n] = 0 ^ 1 .... ^ n = [n, 1, n + 1, 0][n % 4]`