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Overview

x402x is the core package of the x402x protocol, extending the x402 core with foundational types for EIP-3009, EIP-2612, and Permit2, Zod schemas, EVM utilities, and verification logic. It’s typically used indirectly by higher-level packages (x402x-fetch / x402x-server / x402x-facilitator / x402x-detector), but can also be imported directly when you need custom orchestration.

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Capabilities

  • Types and Zod schemas: PaymentRequirements, PaymentPayload, Response402, etc.
  • EVM utilities: EIP-2612 Permit, EIP-3009, and Permit2 signing and verification
  • Validation logic: amount/network/signature/nonce checks
  • Modular design: shared, schemes, client, verify, facilitator, types

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Install

npm i x402x@beta

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Modules and exports

import type { PaymentRequirements, PaymentPayload, Response402 } from "x402x/types";
Other common entry points: 
// Shared EVM utilities
import { getChainId, getNetworkName } from "x402x/shared/evm";

// Scheme utilities (exact)
import { createExactPaymentRequirements, validateExactPayment } from "x402x/schemes";

// Verification utilities
import { verifyPermitSignature, verifyEIP3009Signature, verifyPermit2Signature } from "x402x/verify";

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When to use directly

  • Import base types/utilities when you need custom verification or orchestration
  • When building a facilitator

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Types and schemas (example)

// PaymentRequirements
interface PaymentRequirements {
  scheme: string;              // "exact"
  network: string;             // "bsc-testnet"
  maxAmountRequired: string;   // amount (wei)
  asset: string;               // token address
  paymentType?: string;        // permit/eip3009/permit2
  resource?: string;
  description?: string;
  mimeType?: string;
  maxTimeoutSeconds?: number;
  outputSchema?: Record<string, unknown>;
  extra?: Record<string, unknown>;
}

// Response402
interface Response402 {
  x402Version: number;           // 1
  accepts: PaymentRequirements[]; // list of acceptable payment requirements
  error?: string;
}
Zod validation: 
import { PaymentRequirementsSchema, Response402Schema } from "x402x/types";

const validated = PaymentRequirementsSchema.parse(unknownData);
const safe = Response402Schema.safeParse(unknownResp);

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Usage examples

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Create a 402 response

import type { Response402, PaymentRequirements } from "x402x/types";

function create402Response(accepts: PaymentRequirements[], error?: string): Response402 {
  return { x402Version: 1, accepts, error };
}

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EVM utilities

import { getChainId, getNetworkName } from "x402x/shared/evm";
const id = getChainId("bsc-testnet"); // 97
const name = getNetworkName(97);      // "bsc-testnet"

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Best practices

  • Use Zod schemas to validate external inputs at runtime
  • Leverage type inference to reduce manual type maintenance
  • Import modules on demand to avoid bundling everything

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Relationship to other packages

  • fetch: generates payment headers and retry logic; depends on core types
  • server: orchestrates creation/verification/settlement; depends on verification and types
  • facilitator: defines payment processing interfaces and return types
  • detector: depends on a small subset of EVM/type utilities

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Resources

  • Source: https://github.com/WTFLabs-WTF/x402x/tree/main/typescript/packages/x402x
  • Standards: EIP-2612, EIP-3009, Permit2