Mento Protocol

Architecture

Mento Protocol is an on-chain AMM for stablecoins on Celo. Key contracts:

The Broker delegates to BiPoolManager, which uses SortedOracles for vAMM pricing.

Supported Tokens (15 Mento Stablecoins)

All Mento tokens use 18 decimals. See packages/shared/src/types/tokens.ts for full list:

• USDm, EURm, BRLm, KESm, PHPm, COPm, XOFm, NGNm, JPYm, CHFm, ZARm, GBPm, AUDm, CADm, GHSm

Plus: USDC (6 decimals), USDT (6 decimals) as base tokens.

Swap Flow

1. Find Route (packages/contracts/src/exchanges.ts)

import { findRoute } from '@autoclaw/contracts';

const route = await findRoute(tokenIn, tokenOut, celoClient);
// Returns ExchangeRoute[] — either 1 hop (direct) or 2 hops (via hub)

Routing strategy:

1. Try direct pair first
2. If no direct pool, try 2-hop via USDm hub
3. If not via USDm, try 2-hop via CELO hub

2. Get Quote (packages/contracts/src/quote.ts)

import { getQuote } from '@autoclaw/contracts';

const quote = await getQuote({
  tokenIn,
  tokenOut,
  amountIn: parseUnits('100', 18),
  tokenInDecimals: 18,
  tokenOutDecimals: 18,
  celoClient,
});
// Returns: { amountOut, rate, route, exchangeId, exchangeProvider }

For multi-hop routes, the quote walks each hop calling Broker.getAmountOut().

3. Build Swap Transaction (packages/contracts/src/swap.ts)

import { buildSwapInTxs, applySlippage } from '@autoclaw/contracts';

const amountOutMin = applySlippage(quote.amountOut, 0.5); // 0.5% slippage

const txs = buildSwapInTxs({
  route: quote.route,
  amountIn,
  amountOutMin,
});
// Returns SwapTxData[] — one tx per hop

4. Token Approval

Before swapping, the user must approve the Broker to spend their tokens:

import { BROKER_ADDRESS } from '@autoclaw/contracts';

// Check allowance, approve if needed
// Use ERC20 approve(BROKER_ADDRESS, amount)

See packages/contracts/src/allowance.ts for approval helpers.

Key Interfaces

interface ExchangeRoute {
  exchangeId: `0x${string}`;
  tokenIn: Address;
  tokenOut: Address;
}

interface QuoteResult {
  amountOut: bigint;
  exchangeProvider: Address;
  exchangeId: `0x${string}`;
  rate: number;
  route: ExchangeRoute[];
}

interface SwapTxData {
  to: Address;
  data: `0x${string}`;
}

Route Cache

getRoutes() caches exchange pools for 5 minutes. Call clearRouteCache() to force refresh.

Important Notes

• Mento stablecoins use 18 decimals; USDC/USDT use 6 decimals — always check with getTokenDecimals()
• Multi-hop swaps require separate transactions per hop (executed sequentially)
• The Broker's swapIn function takes: exchangeProvider, exchangeId, tokenIn, tokenOut, amountIn, amountOutMin
• Slippage is applied only to the final hop; intermediate hops use 0n for minOut
• Token addresses are in packages/shared/src/types/tokens.ts (MENTO_TOKEN_ADDRESSES, ALL_TOKEN_ADDRESSES)
• Contract addresses are in packages/contracts/src/addresses.ts