Is there an API that can be use to create a decentralized wallet

Please, is there a Trusted and reliable API that I can use to create a decentralized wallet?
Where my users can:

  1. Generate their Wallet Addresses that will have a private key and 12 secret phrase
  2. Can receive and send Crypto Coins and tokens
  3. and Work on different networks Just like Trustwallet

Using an API wouldn’t make it very decentralized. Here’s one I found to create wallets.

For points 2 and 3, you will still need some sort of interface or app for users anyway, like MetaMask.