Borrow (CDP)

The Mento SDK v3 supports trove management via the Mento CDP system (Liquity v2 fork): open, adjust, and close troves; repay debt; read trove data and system params; and predict upfront fees before opening.

In Mento CDPs, USDm is the collateral: you lock USDm and borrow another stable (e.g. GBPm). The SDK identifies each CDP system by the debt token (the stable you borrow). See CDPs in Smart Contracts for an overview and the Liquity v2 docs for full mechanics.

---

Create the client

import { Mento, ChainId } from '@mento-protocol/mento-sdk'
import { parseUnits } from 'viem'

const mento = await Mento.create(ChainId.CELO)

---

Open a trove

Lock USDm as collateral and borrow the debt stable (e.g. GBPm). Pass the debt token symbol (the stable you borrow) to identify the CDP system. You specify owner, collateral amount (USDm), debt amount (e.g. GBPm), interest rate, and max upfront fee:

// Borrow GBPm against USDm collateral (debt token = GBPm)
const openTx = await mento.borrow.buildOpenTroveTransaction('GBPm', {
  owner: ownerAddress,
  ownerIndex: 0,
  collAmount: parseUnits('10000', 18),   // USDm collateral
  boldAmount: parseUnits('1000', 18),    // GBPm to borrow
  annualInterestRate: parseUnits('0.05', 18),   // 5%
  maxUpfrontFee: parseUnits('100', 18),
})

Send the returned transaction(s) with your viem wallet (approvals first if needed, then the open-trove tx).

---

Predict upfront fee (before opening)

Estimate the upfront fee for a given borrow amount and interest rate so users can see cost before committing. Pass the debt token (e.g. GBPm) and the amount to borrow:

const fee = await mento.borrow.predictOpenTroveUpfrontFee(
  'GBPm',
  parseUnits('1000', 18),
  parseUnits('0.05', 18)
)

---

Get trove data

Read a specific trove’s state (collateral, debt, etc.). Pass the debt token (e.g. GBPm):

const trove = await mento.borrow.getTroveData('GBPm', troveId)

---

Get system parameters

Read CDP system params (e.g. min/max collateral, rates, caps) for a CDP system. Pass the debt token (e.g. GBPm):

const params = await mento.borrow.getSystemParams('GBPm')

Use this to validate user inputs or display protocol limits in your UI.

---

Adjust and close troves

The SDK also supports adjusting an existing trove (add/remove collateral, borrow more, repay) and closing a trove. Use the corresponding mento.borrow methods (e.g. buildAdjustTroveTransaction, buildCloseTroveTransaction—check the package exports for exact names) with the same pattern: they return transaction params you send with your viem wallet.

---

Summary

Operation	Service method
Open trove	mento.borrow.buildOpenTroveTransaction('GBPm', { ... }) — debt token = what you borrow
Predict upfront fee	mento.borrow.predictOpenTroveUpfrontFee('GBPm', boldAmount, rate)
Trove data	mento.borrow.getTroveData('GBPm', troveId)
System params	mento.borrow.getSystemParams('GBPm')
Adjust / close / repay	See mento.borrow exports for buildAdjustTroveTransaction, buildCloseTroveTransaction, etc.

All builders return transaction (and optional approval) params; you send them with a viem wallet. Runnable examples: mento-sdk-examples.