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X402 API

Implements HTTP-native x402 payment flows for clients, resource servers, and facilitators across supported networks.

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Install X402 API

Pick your client, then add it in one click or paste the config.

STDIOPython
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "x402-api-2": {
      "command": "uvx",
      "args": [
        "x402"
      ]
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Install not yet sandbox-tested— we haven't run this command through our automated sandbox yet. Not a red flag; we're working through the catalog.

Overview

The x402-api MCP server is based on x402, an open standard for attaching payments to HTTP resource requests. It defines a flow in which clients receive payment requirements, submit signed payment payloads, and obtain resources after verification and settlement. The protocol supports multiple payment schemes and network implementations, with reference SDKs for TypeScript, Python, and Go. Reach for it when an HTTP API needs a documented payment-required flow rather than an external checkout process.

Use cases

  • Protect HTTP API routes with payment requirements
  • Request paid resources through signed payment payloads
  • Verify payments through local logic or a facilitator
  • Settle supported payments on a blockchain
  • Add payment schemes to client-server request flows

Key features

  • HTTP 402 payment-required responses
  • Client payment payload creation
  • Local or facilitator-based verification
  • Direct or facilitator-based settlement
  • Extensible scheme and network model
  • TypeScript, Python, and Go reference SDKs

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked Today

Recent health check succeeded.

4/4 checks healthy over the last 40d

Supply-chain signal

1 high-severity advisory on record for this package. Most advisories affect transitive dependencies and may not be exploitable in this server's actual usage — this is a directional signal, not a security audit.

Critical 0High 1Medium 0Low 0

Scanned 14d ago via OSV.dev · x402 (PyPI)

How X402 API works

What x402-api does

The x402-api MCP server is associated with x402, an open standard for internet-native payments over HTTP. The protocol connects three roles: a client requesting a resource, a resource server providing an API or other HTTP resource, and a facilitator that can verify and settle payments for supported networks and schemes.

Rather than defining one currency or blockchain, x402 describes payment requirements and payloads that can be implemented across networks. Its stated scope includes crypto and fiat networks, stablecoins, tokens, and other forms of value, subject to the available scheme and network implementations. The material specifically describes an exact scheme for transferring a specified amount.

How it works

A client first requests a protected resource. The resource server can respond with HTTP status 402 Payment Required and provide a base64-encoded PaymentRequired object in the PAYMENT-REQUIRED header. The client selects an accepted payment requirement and creates a PaymentPayload for its scheme and network.

The client then repeats the request with the payload in the PAYMENT-SIGNATURE header. The resource server verifies the payload locally or sends it to a facilitator's /verify endpoint. If verification succeeds, the server fulfills the request. Settlement can occur directly on a blockchain or through a facilitator's /settle endpoint. After successful execution, the resource server returns the requested content and may include a base64-encoded settlement response in the PAYMENT-RESPONSE header.

The x402-api MCP server therefore fits workflows where payment is part of the normal request and response exchange. The protocol also allows servers flexibility around when verification and settlement occur, trading response speed against payment guarantees.

Setup and configuration

The repository provides reference packages rather than MCP-client setup instructions. TypeScript users can install the core, EVM, SVM, and fetch packages for a minimal client, or use the Express package for a minimal server. Additional TypeScript packages cover Axios, Hono, Next.js, a paywall, and extensions. Python installation uses the x402 package, while Go projects can import the repository's Go module.

Those details should be confirmed from the repository's implementation and examples before deployment.

Tools and capabilities

The documented capabilities are protocol-level:

  • Declare accepted payment requirements for HTTP routes.
  • Return payment-required responses using HTTP semantics.
  • Create client payment payloads for supported scheme and network pairs.
  • Verify payloads locally or through a facilitator.
  • Settle payments locally or through a facilitator.
  • Extend implementations to additional schemes and networks.

Limitations and notes

Support is not automatic for every network and scheme. Clients and facilitators must explicitly support the selected pair, and scheme behavior can vary by blockchain. The documentation describes exact as the first shipping scheme and mentions upto as a theoretical example, so the availability of other schemes should not be assumed.

It also does not establish that the marketing, content, and outreach endpoints mentioned in the listing are implemented. Use the repository's specifications and examples to validate those capabilities before relying on them.

Read the full README View source on GitHub

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Frequently Asked Questions about X402 API

x402-api is an MCP server that connects agents to HTTP resources using x402 payment flows and provides payment-related capabilities for clients, resource servers, and facilitators.

It uses HTTP 402 responses to return payment requirements. A client selects a supported scheme and network, creates a payment payload, and retries the request with that payload in the PAYMENT-SIGNATURE header.

Yes, the protocol supports facilitator-based verification and settlement. A resource server can send payment data to the facilitator's /verify and /settle endpoints, although it may also verify locally or interact with a blockchain directly.

The repository provides reference SDKs for TypeScript, Python, and Go. TypeScript packages include client and server integrations, Python installs through the x402 package, and Go uses the repository's Go module.

No, support depends on explicit implementations for each scheme and network pair. The documentation describes the exact scheme and says the protocol is extensible, but clients and facilitators must support the selected combination.

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