Xenarch Mcp

io.github.xenarch-aiPublished by GitHub account xenarch-aiv1.3.1Updated Oct 24, 2026

Xenarch — x402 MCP server for AI agent payments. Non-custodial, USDC on Base L2.

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Overview

AI-generated overview

A local MCP server that lets an AI assistant detect x402 payment gates and pay for gated web content with USDC micropayments on Base.

What you can do
Check whether a URL or domain has an x402 payment gate and read its price, asset, network and seller wallet; pay a gated URL or a Xenarch pay-link in USDC and get back the transaction hash and content; review past payments and totals for the wallet; manage the spending agent's caps, scope rules, pause switch and API keys; create, list and revoke merchant pay-links, view payments and subscribers, and update the merchant profile and domain verification.
When to use it
Use it when an assistant needs to fetch content or APIs that answer with HTTP 402 and you are willing to pay small USDC amounts per request, or when you operate a Xenarch agent or merchant account and want to manage caps, scope and pay-links from the chat client.
Requirements
Runs locally via npx as a Node.js package. Needs a funded wallet: XENARCH_PRIVATE_KEY (a hex wallet private key, auto-generated on first run if omitted) holding USDC on Base. Payments also require XENARCH_API_TOKEN, an xa_live_ agent key; without it payments are refused. Optional: XENARCH_MAX_PAYMENT_USD, XENARCH_NETWORK, XENARCH_RPC_URL, PORT, TRANSPORT. Control-plane and merchant tools need a SIWE session created with the xenarch agent login command.
Before you install
The server holds a wallet private key (XENARCH_PRIVATE_KEY) and spends real USDC on-chain; every payment is irreversible. The local per-call cap XENARCH_MAX_PAYMENT_USD defaults to 1.00 and is the only spending ceiling in standalone mode, and setting it to 0 removes the cap. Tools can change spending caps, scope rules, API keys, pay-links and merchant profile data, and some privileged actions need confirm: true. A SIWE session token is stored in the user's Xenarch config file.

Installation

In SourceWeft

  1. Open Xenarch Mcp in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

Xenarch — x402 MCP server for AI agent payments

[npm] [License: MIT]

Xenarch is a non-custodial x402 MCP server. AI agents — Claude, Cursor, LangChain, CrewAI — pay for HTTP 402—gated APIs and content with USDC micropayments on Base L2. No API keys, no subscriptions, no credit card on file. The agent wallet never needs ETH; USDC is the only token it ever holds. Payments settle on-chain: agent wallet → publisher wallet, direct. 0% Xenarch fee — there's no Xenarch contract in the money flow.

What makes Xenarch different

Cloudflare Pay-Per-CrawlStripeTollBitVercel x402-mcpOther x402 MCP serversXenarch
Works on any host× (Cloudflare only)✓× (enterprise)Vercel-first✓✓
Non-custodial×××platform-routedvaries✓ direct USDC transfer
Agent needs ETHn/an/an/avariesvaries✓ never
Feeplatform rate2.9% + $0.30platform rateplatform ratevaries0%, structurally
Open standardproprietaryproprietaryproprietaryx402x402x402 + pay.json (authored by Xenarch)
Publisher monetization✓ (Cloudflare-gated)✓ (any stack)✓ (enterprise only)××✓ (any stack)

How it works

1. Discover    xenarch_check_gate("example.com")               → { gated: true, accepts: [...] }
2. Pay         xenarch_pay("example.com")               → x402-fetch signs an EIP-3009 USDC transferWithAuthorization               → Settlement goes on-chain               → Re-fetches the resource with proof of payment               → { tx_hash, content }

No API keys. No signup. The agent wallet only ever needs USDC — no ETH, no gas coin of any kind. Xenarch never holds funds and there is no Xenarch contract between the agent and the publisher.

MCP tools

29 tools across three groups. Group 1 (discovery & payments) works with just a wallet. Groups 2 and 3 (control plane + merchant) manage your Xenarch account and need a SIWE session — run xenarch agent login once (see Account tools auth).

1. Discovery & payments — agent wallet only

ToolDescription
xenarch_check_gateCheck if a URL/domain has an x402 payment gate. Returns the accepted payment requirements — price, asset, network, seller wallet.
xenarch_payPay for an x402-gated URL. Signs an EIP-3009 USDC transfer, settles on-chain, returns the tx hash and the gated content.
xenarch_pay_linkPay a Xenarch pay-link by id (pay.xenarch.com/l/<id>): fetches the envelope, settles USDC on Base, confirms with the link.
xenarch_get_historyView past payments made by this wallet (totals, per-domain, pagination).

2. Agent control plane — manage your spending agent (SIWE session)

Caps, scope, kill-switch, and API keys for the operator's agent. Privileged (loosening) operations require confirm: true; tightening is free.

ToolDescription
xenarch_agent_loginBrowser-wallet sign-in to the control plane. Returns a link; open it, approve, call again to finish. The 7-day session powers every other xenarch_agent_* tool.
xenarch_agent_statusAgent profile (name, paused state) + spend summary for a period. Read-only.
xenarch_agent_get_capsRead spending caps (per-tx, daily, monthly) + remaining headroom. Read-only.
xenarch_agent_set_capsSet caps in USD (none disables an axis). Raising/removing a cap needs confirm: true; tightening is free.
xenarch_agent_reset_day_capReset today's daily-spend counter to the full daily cap.
xenarch_agent_get_scopeRead scope: default posture (allow/deny) + the rule list. Read-only.
xenarch_agent_add_scope_ruleAdd an allow/deny rule. deny tightens (free); allow loosens (needs confirm).
xenarch_agent_remove_scope_ruleRemove a rule by id/prefix. Removing a deny loosens scope (needs confirm).
xenarch_agent_set_default_scopeSet the posture for unmatched URLs. deny tightens; allow loosens (needs confirm).
xenarch_agent_pauseKill switch — block all of the agent's payments immediately. No confirm.
xenarch_agent_resumeLift the pause (needs confirm).
xenarch_agent_list_keysList the agent's xa_live_ API keys (id, label, last-used, revoked). Never returns plaintext. Read-only.
xenarch_agent_create_keyIssue a new xa_live_ key (plaintext returned once). Needs confirm.
xenarch_agent_rotate_keyRotate a key by id/prefix — invalidates the old secret, returns a new one once. Needs confirm.
xenarch_agent_revoke_keyPermanently revoke a key by id/prefix. Needs confirm.
xenarch_agent_get_receiptsList the agent's payment receipts with filters (period, status, source, domain). Read-only.

3. Merchant — get paid (SIWE session)

Create and manage pay-links, see payments and subscribers, set the merchant profile. Same SIWE session as the control plane.

ToolDescription
xenarch_create_linkCreate a pay-link. VALIDATE-FIRST: mode:'validate' reports missing fields; then mode:'create' + confirm:true signs + creates. Amount is USDC (max 1.00).
xenarch_list_linksList the merchant's pay-links (newest first), cursor-paginated. Read-only.
xenarch_get_linkGet one pay-link's detail (status, params, stats) by id. Read-only.
xenarch_revoke_linkRevoke a pay-link by id so it can no longer be paid. Needs confirm.
xenarch_list_paymentsList payments received across the merchant's links (newest first), cursor-paginated. Read-only.
xenarch_list_subscribersList subscribers across subscription links, with filters (link_id, status, mode). Read-only.
xenarch_get_merchant_profileGet the merchant profile (issuer identity, domain-verification status). Read-only.
xenarch_update_merchant_profileUpdate the merchant profile (name, site, email, address, tax id, brand color, logo, payout rhythm). Whole-state upsert.
xenarch_verify_domainVerify the merchant's domain via its _xenarch.<site> DNS TXT record. Set the site first via xenarch_update_merchant_profile.

Account tools auth

  • Payments (group 1) need a funded wallet (XENARCH_PRIVATE_KEY) and a control-plane link (XENARCH_API_TOKEN) — the official MCP refuses to pay without the token (XEN-480: an unlinked agent has no caps). A local per-call cap (XENARCH_MAX_PAYMENT_USD, default $1) applies on top of the managed per-tx / daily / monthly caps.
  • Control plane + merchant (groups 2–3) need a SIWE session. Run xenarch agent login once — it writes a 7-day session_token to ~/.xenarch/config.json, which the MCP server reads automatically. Re-run when it expires, or call xenarch_agent_login directly from your client.
  • Set XENARCH_API_TOKEN (an xa_live_ agent key) so xenarch_pay is enforced against your managed caps/scope and every MCP payment shows up in the dashboard receipts feed. The dashboard is free — sign in with your wallet at dash.xenarch.dev (just a signature, nothing moves) for per-tx / daily / monthly caps, scope rules, a kill switch, and full history. Without the token, xenarch_pay refuses to pay (fail-closed) so an unlinked agent can't settle uncapped. Note: the dashboard sign-in wallet is your identity — separate from the agent's local spending wallet.

Example responses

xenarch_check_gate
json
{  "gated": true,  "gate_id": "7f3a1b2c-9d4e-4a8b-b6f1-2c3d4e5f6a7b",  "accepts": [    {      "scheme": "exact",      "network": "base",      "maxAmountRequired": "3000",      "resource": "https://example.com/article",      "payTo": "0xabc123...publisher_wallet",      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",      "maxTimeoutSeconds": 60    }  ],  "seller_wallet": "0xabc123...publisher_wallet",  "network": "base",  "asset": "USDC"}
xenarch_pay
json
{  "success": true,  "gate_id": "7f3a1b2c-9d4e-4a8b-b6f1-2c3d4e5f6a7b",  "tx_hash": "0xdef456...abc789",  "seller_wallet": "0xabc123...publisher_wallet",  "url": "https://example.com/article",  "wallet": "0x123...your_wallet",  "content": "...gated content here..."}
xenarch_get_history
json
{  "payments": [    {      "domain": "example.com",      "amount_usd": "0.003",      "tx_hash": "0xdef456...abc789",      "paid_at": "2026-04-10T14:35:00Z"    }  ],  "total_spent_usd": "0.003000",  "count": 1,  "wallet": "0x123...your_wallet"}

HTTP 402 — the unused status code that x402 finally activates

HTTP 402 Payment Required is a status code reserved in the HTTP spec since 1997 for machine-to-machine payment. It went unused for decades because there was no open protocol for how a client should pay a 402 response.

x402 is that protocol: a server returns HTTP 402 with a signed price and payment details, the client signs a USDC micropayment on Base L2, and retries the request with proof of payment. Xenarch's MCP server automates both halves for AI agents — it reads the 402 challenge, signs the payment via x402-fetch, and replays the request, returning the on-chain tx hash plus the gated content.

Learn more: the x402 spec defines the payment handshake; pay.json (authored by Xenarch) is the companion open standard for machine-readable pricing served at /.well-known/pay.json — think robots.txt for payments.

API monetization with HTTP 402

Xenarch is an API monetization primitive built on the HTTP 402 spec. Unlike API gateway monetization platforms (Apigee, Kong, AWS API Gateway) that require subscriptions, dashboards, and API keys, Xenarch lets any API charge per request with no account creation and no key provisioning — the caller pays USDC on Base L2, the API verifies the on-chain transaction, access is granted.

For publishers, this means:

  • No integration with Stripe/card processors
  • No subscription plans, pricing tiers, or quota dashboards
  • No custodial balance held by a platform
  • Per-request pricing that works for human users, bots, and AI agents uniformly
  • API monetization that settles on-chain in real time

The Python SDK includes a one-decorator FastAPI middleware; see xenarch-sdks/python for publisher integration.

Setup

  1. Configure your wallet:
bash
mkdir -p ~/.xenarchcat > ~/.xenarch/wallet.json << 'EOF'{  "privateKey": "0xYOUR_PRIVATE_KEY"}EOFchmod 600 ~/.xenarch/wallet.json
  1. Add to Claude Code:
bash
claude mcp add xenarch -- npx @xenarch/agent-mcp

Or add the same JSON to any MCP client's config file:

  • Claude Desktop — ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) / %APPDATA%\Claude\claude_desktop_config.json (Windows)
  • Cursor — ~/.cursor/mcp.json (global) or .cursor/mcp.json (per-project)
  • Cline (VS Code) — the MCP Servers panel → "Configure MCP Servers", or cline_mcp_settings.json
json
{  "mcpServers": {    "xenarch": {      "command": "npx",      "args": ["@xenarch/agent-mcp"],      "env": {        "XENARCH_PRIVATE_KEY": "0xYOUR_PRIVATE_KEY",        "XENARCH_API_TOKEN": "xa_live_…optional, enforces caps/scope"      }    }  }}

  1. Fund the wallet with USDC on Base. That's it — no ETH, no other token needed.

  2. (Optional) To use the control-plane + merchant tools, run xenarch agent login once to create a SIWE session.

Environment variables

VariableDefaultDescription
XENARCH_PRIVATE_KEY—Wallet private key (overrides config file)
XENARCH_API_TOKEN—Required. Agent xa_live_ key. Enforces xenarch_pay against your caps/scope and feeds the dashboard receipts. Without it, xenarch_pay refuses to pay (fail-closed).
XENARCH_RPC_URLhttps://mainnet.base.orgBase RPC endpoint
XENARCH_API_BASEhttps://xenarch.devXenarch platform API
XENARCH_NETWORKbaseNetwork (base or base-sepolia)
XENARCH_MAX_PAYMENT_USD1.00Local per-call payment cap (USDC). The only spending ceiling in standalone mode — xenarch_pay refuses any single payment above it. Set 0 to remove the cap. For managed per-tx / daily / monthly caps, connect XENARCH_API_TOKEN.

The control-plane + merchant tools don't use an env var for auth — they read the SIWE session_token that xenarch agent login writes to ~/.xenarch/config.json.

Examples

See xenarch-examples for working integration examples — Python agents, LangChain, CrewAI, Claude Desktop setup, and publisher middleware.

Development

bash
npm installnpm run build

Structure

packages/  shared/    — Payment logic, types, config (reused across servers)  agent/     — MCP server for AI agents

FAQ

How does Claude pay for APIs with Xenarch? Install the Xenarch MCP server (claude mcp add xenarch -- npx @xenarch/agent-mcp), give it a wallet, and Claude resolves any HTTP 402 response automatically with a USDC micropayment on Base L2.

Does Xenarch work with Cursor, LangChain, or CrewAI? Yes. Xenarch exposes an MCP server that any MCP-compatible client can use — Claude Code, Claude Desktop, Cursor, Cline, LangChain, CrewAI, and any other client that speaks Model Context Protocol.

Is FastAPI supported for publishers? Yes, via the Python SDK (pip install xenarch[fastapi]) — a one-decorator middleware returns HTTP 402 with the price and verifies the on-chain payment. See xenarch-sdks/python.

Is Xenarch custodial? No. Payments settle on-chain as a direct USDC transfer from the agent wallet to the publisher wallet. Funds never touch Xenarch infrastructure and there is no Xenarch contract in the money flow.

Does the agent need ETH for gas? No. USDC is the only token the agent wallet ever needs. Fund it with USDC and you're done — no ETH, no other gas coin.

What's the fee? 0%, structurally. Xenarch never sits in the money flow — there's no Xenarch contract that could charge a fee.

What's the maximum payment per call? $1 USD.

What is x402? x402 is an open protocol for HTTP 402 Payment Required. A server returns 402 with a price, the client signs a USDC micropayment on Base L2 (or other supported chain), and retries the request with proof of payment.

What is HTTP 402? HTTP 402 Payment Required is a status code reserved in the HTTP spec since 1997 for machine-to-machine payment. x402 is the open protocol that finally uses it.

How does Xenarch compare to Cloudflare Pay-Per-Crawl? Cloudflare Pay-Per-Crawl only works for sites behind Cloudflare and is custodial. Xenarch works on any host and is non-custodial — publishers are paid directly on-chain.

How does Xenarch compare to TollBit? TollBit is enterprise-licensing focused. Xenarch is self-serve, non-custodial, and works for the long tail of publishers and any AI agent without enterprise contracts.

Links

License

MIT

Source: README.md at commit 68cbdf1

Tools

0
SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

1
  1. v1.3.1LatestSep 16, 2026

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