Exact and Upto

The exact and upto schemes let you pay per request without pre-funding a channel. Each call results in an on-chain transfer.

Exact

Fixed-price payments. The server advertises a price, you sign for that exact amount, and the facilitator settles an on-chain transfer.

import ComposeSDK, { createPrivateKeyX402EvmWallet } from "@compose-market/sdk";

const { x402Signer } = createPrivateKeyX402EvmWallet({
  privateKey: "0xYourPrivateKey",
  schemes: ["exact"],
});

const sdk = new ComposeSDK({
  userAddress: "0xYourWalletAddress",
  chainId: 43113,
});

Use exact for:

One-shot API calls
Fixed-price resources (file downloads, gated pages)
When you don’t want to pre-fund a channel

The signer does not need an RPC URL for exact — no on-chain state to read.

Upto

Usage-based payments. The server advertises a maximum price, you sign a Permit2 authorization for that maximum, and the server charges the actual usage after processing.

const { x402Signer } = createPrivateKeyX402EvmWallet({
  privateKey: "0xYourPrivateKey",
  rpcUrl: "https://avax-fuji.g.alchemy.com/v2/YourRpcKey",
  schemes: ["upto"],
});

Use upto for:

LLM token billing (charge for actual tokens used)
Compute-time billing
Dynamic data queries where the cost varies

The settled amount is always less than or equal to the signed maximum. The server uses settlement overrides to charge the actual amount:

// The SDK receives the final amount in the receipt
const result = await stream.next();
console.log(result.receipt.bills[0].total); // actual amount charged

Register multiple schemes

You can register all three schemes at once — the SDK picks the right one based on what the server advertises:

const { x402Signer } = createPrivateKeyX402EvmWallet({
  privateKey: "0xYourPrivateKey",
  rpcUrl: "https://avax-fuji.g.alchemy.com/v2/YourRpcKey",
  schemes: ["batch-settlement", "upto", "exact"],
});

Transfer methods

The EVM implementation supports two transfer methods:

Method	Description
`eip3009`	Uses token-native `transferWithAuthorization`. Default for USDC.
`permit2`	Uses Uniswap Permit2 plus an x402 proxy. Supports any ERC-20.

The SDK automatically selects the right method based on the token’s capabilities.

Getting Started

Payments

Agent Streaming

Tools

Slash Commands

Channels

Memory

Inference

Guides

Exact

Upto

Register multiple schemes

Transfer methods

​Exact

​Upto

​Register multiple schemes

​Transfer methods

Exact

Upto

Register multiple schemes

Transfer methods