We hear a lot about APIs as financial institutions open up their services for public access, but webhooks can be just as useful for user experience in personal finance management.
APIs are more passive whereas webhooks are more pro-active.
This makes a difference from a programmatic point of view, which then affects user experience.
You can imagine this difference with e-mail for example.
Imagine a time before push notifications. Without push notification, the manifest practice is to "Check mail". Remember those quaint days when we used to push that Send/Receive button? That's API call for you.
While we can code applications in such a way as to check an API very often, it's not very bandwidth-compute-energy efficient.
Webhooks are much better. Like push notification, applications gets notified when a transaction happens and changes its state accordingly.
Along with the change of state, any other triggers or reactive components can then come alive, a much better pattern :)