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Crossmint offers stablecoin APIs aimed at enterprises, including cross-chain flows. Builders use it to add stablecoin payments to an application without building the payment rails.

The Lido Ethereum SDK is the official package for staking and managing stETH and wstETH through the Lido protocol. Builders install it to add staking to an application without writing the Lido contract calls by hand.

The Machine Payments Protocol SDK, published as mppx by the wevm team behind viem and wagmi, is a TypeScript implementation of an agent payments specification. Builders install it to let a service or agent pay and charge programmatically.

Request Network is a protocol and JavaScript library for creating, paying, and tracking crypto invoices and payment requests onchain. Builders install the client library to add invoicing to their own application.

Stripe Crypto Onramp is an embeddable fiat-to-crypto onramp SDK for web, iOS, Android, and React Native that delivers purchased crypto to a user's wallet. Builders embed it so users can fund a wallet with a card instead of transferring in.

web3-ethereum-defi is a Python library for DeFi integration and data research, with wrappers for Uniswap, Aave, Chainlink, and USDC on top of web3.py. Python builders import it instead of writing those protocol wrappers themselves.