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Trails lets you compose multiple onchain operations: bridge, swap, deposit, stake, or any contract call, into a single user-facing transaction. The user approves once. Trails handles routing, execution, and gas across every step. This is the foundation for any flow where funds need to move and land in a specific protocol state: a yield vault, a liquidity position, a staking contract, a cross-chain swap. The source chain, token, and amount are flexible. The destination action is whatever your protocol requires.

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How it works

User approves once
  → Trails quotes the full route
      → Funds bridge and swap to the destination chain and token
          → Trails executes your encoded contract call with the exact arrived amount
              → User lands in the desired protocol state
TRAILS_ROUTER_PLACEHOLDER_AMOUNT stands in for the arrived amount in your calldata. Trails substitutes the real figure at execution time, so slippage and bridge variance are absorbed automatically.

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Encoding a composable action

Pass destinationCalldata with the encoded function call for whatever action you want executed on arrival. The example below deposits into an ERC-4626 yield vault, but the same pattern works for any protocol: 
import { encodeFunctionData } from "viem";
import { TRAILS_ROUTER_PLACEHOLDER_AMOUNT } from "0xtrails";

const depositCalldata = encodeFunctionData({
  abi: [{
    type: "function",
    name: "deposit",
    inputs: [
      { name: "assets", type: "uint256" },
      { name: "receiver", type: "address" },
    ],
    outputs: [{ name: "shares", type: "uint256" }],
  }],
  functionName: "deposit",
  args: [TRAILS_ROUTER_PLACEHOLDER_AMOUNT, "0xUserAddress"],
});

const response = await fetch("https://trails-api.sequence.app/rpc/Trails/QuoteIntent", {
  method: "POST",
  headers: { "Content-Type": "application/json", "X-Access-Key": "YOUR_API_KEY" },
  body: JSON.stringify({
    ownerAddress: "0xUserAddress",
    originChainId: 1,            // any supported chain
    originTokenAddress: "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48", // any token
    destinationChainId: 137,
    destinationTokenAddress: "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359", // USDC on Polygon
    destinationToAddress: "0xYourProtocolAddress",
    destinationTokenAmount: "100000000", // 100 USDC (6 decimals)
    destinationCalldata: depositCalldata,
    tradeType: "EXACT_OUTPUT",
  }),
});

const { intent } = await response.json();
The user can be on Ethereum mainnet holding ETH, USDT, or any supported token. Trails bridges to Polygon, swaps to USDC, and executes the deposit in one flow.

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What you can compose

Any protocol interaction that takes a token amount as input works with this pattern:
ActionABI functionNotes
Yield vault depositdeposit(uint256 assets, address receiver)ERC-4626 standard
Liquidity provisionaddLiquidity(...)AMM-specific ABI
Stakingstake(uint256 amount)Protocol-specific
Lending supplysupply(address asset, uint256 amount, ...)Aave-style
Custom contract callAny payable functionEncode via encodeFunctionData

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Widget integration

For drop-in UI, pass toCalldata to the Trails Widget. The widget handles the full funding and action flow: 
import { TrailsWidget } from "0xtrails/widget";

<TrailsWidget
  apiKey="YOUR_API_KEY"
  mode="fund"
  toAddress="0xYourProtocolAddress"
  toChainId={137}
  toToken="USDC"
  toCalldata={depositCalldata}
  onCheckoutComplete={({ sessionId }) => updateUserState(sessionId)}
>
  <button>Deposit</button>
</TrailsWidget>

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Example: yield accounts

One common use of composable actions is offering savings accounts in a fintech or neobank app. Users deposit USDC into a yield vault. The entire flow (bridge, swap, deposit) happens in a single tap, with no gas, no wallet management, and no protocol knowledge required from the user.

Offer yield accounts to your users

Step-by-step guide: wallet setup, Morpho vault deposit, permit signing, and withdraw flow.

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Next steps

Fund from Anywhere

Let users fund your protocol from any token, chain, credit card, or bank account.

Smart Sessions

Automate recurring actions without per-transaction prompts.

Trails API reference

Full endpoint reference for QuoteIntent, CommitIntent, and ExecuteIntent.