STON.fi is a non-custodial AMM protocol on TON. It lets users swap tokens directly with each other through smart contracts, instead of going through a central company holding their funds. There's no broker, no order book, and no account to create — you connect a wallet, sign a transaction, and the swap happens on-chain.
How STON.fi handles a swap
STON.fi uses an automated market maker (AMM) model. Instead of matching buyers with sellers, it pools two tokens together in a smart contract and prices them with a formula. The most common version is:
x × y = k
…where x and y are the two token quantities in the pool and k is a constant. When you swap one token for the other, the ratio shifts, the price moves accordingly, and a small fee is added to the pool — which is what pays liquidity providers.
The two roles in the protocol
- Swappers swap tokens through the pool and pay a small fee for the convenience.
- Liquidity providers (LPs) provide token pairs to the pool, and their LP positions accrue a share of those fees over time.
STON.fi offers several pool types beyond the standard one — including Stableswap pools tuned for stablecoin pairs and WCPI / WStableswap pools that allow custom token weights. For the full breakdown, see Pool types & strategies.