xenarch 0.2.2

Xenarch is a non-custodial x402 MCP server. Claude, Cursor and any MCP client pay for HTTP 402–gated content with USDC micropayments on Base L2. Direct agent-to-publisher settlement. 0% fee, no contract, facilitator-agnostic.

xenarch — Python SDK for Xenarch's x402 MCP server

Xenarch is a non-custodial x402 MCP server. Claude, Cursor and any MCP client pay for HTTP 402–gated content with USDC micropayments on Base L2. Direct agent-to-publisher settlement. 0% fee, no contract, facilitator-agnostic.

This package is the Python SDK and FastAPI middleware. Use it to (a) let LangChain / CrewAI / FastAPI agents pay any x402-gated URL, or (b) gate your own FastAPI endpoints behind HTTP 402.

Unlike Cloudflare Pay-Per-Crawl / TollBit

	Cloudflare Pay-Per-Crawl	TollBit	Xenarch
Works on any host	❌ (Cloudflare only)	❌ (enterprise)	✅
Non-custodial	❌	❌	✅ (agent-to-publisher direct, no Xenarch contract)
Fee	Platform rate	Platform rate	0% — no Xenarch contract that can charge a fee
Open standard	proprietary	proprietary	x402 + pay.json (open)

Settlement happens through any spec-compliant third-party x402 facilitator (PayAI, xpay, Ultravioleta DAO, x402.rs). Xenarch is never in the money flow.

Install

# For LangChain agents paying x402-gated APIs
pip install xenarch[langchain,x402]

# For publishers (FastAPI middleware)
pip install xenarch[fastapi]

Quick start

Agent: pay for x402-gated content

from decimal import Decimal

from xenarch.tools import XenarchPay, XenarchBudgetPolicy

tool = XenarchPay(
    private_key="0x...",
    budget_policy=XenarchBudgetPolicy(
        max_per_call=Decimal("0.05"),
        max_per_session=Decimal("1.00"),
    ),
)

# Use directly, or register with any LangChain agent.
print(tool.invoke("https://example.com/premium-article"))

XenarchPay is a LangChain BaseTool over the neutral x402-agent pay loop, plus Xenarch's signed-receipt and reputation extras. Settles USDC on Base via EIP-3009 — never custodial.

Publisher: gate a FastAPI endpoint behind HTTP 402

from fastapi import FastAPI
from xenarch import XenarchMiddleware

app = FastAPI()
app.add_middleware(
    XenarchMiddleware,
    site_token="your-site-token",
    protected_paths=["/premium/*"],
)

Or use the decorator:

from xenarch import require_payment

@app.get("/premium/article")
@require_payment(price_usd="0.05")
async def premium_article():
    return {"content": "This is premium content"}

The decorator returns HTTP 402 with the price when called without payment, verifies the USDC transfer to the publisher's wallet via a third-party x402 facilitator, and grants access with a time-limited Bearer token.

Env vars

Var	Purpose
XENARCH_API_BASE	Override the Xenarch API base URL (default: production)
XENARCH_PRIVATE_KEY	Agent wallet private key for signing USDC payments
XENARCH_MAX_PAYMENT_USD	Agent-configurable per-call cap. Default unbounded
XENARCH_FACILITATOR_URL	Override the x402 facilitator endpoint (default: ranked fallback list)

FAQ

How does Claude pay for APIs with Xenarch? Install the Xenarch MCP server, give it a wallet, and Claude resolves any HTTP 402 response automatically with a USDC micropayment on Base L2.

Is Xenarch custodial? No. Payments settle direct from the agent's wallet to the publisher's wallet via a third-party x402 facilitator. Funds never touch Xenarch infrastructure — there is no Xenarch contract in the money flow.

What's the fee? 0%. There is no Xenarch contract that can charge a fee — the architecture is structurally zero-fee, not a policy promise.

What's the max payment? Agent-configurable. Default is unbounded; set XENARCH_MAX_PAYMENT_USD to cap per-call spend.

Links

• Learn more: https://xenarch.com
• GitHub: https://github.com/xenarch-ai/xenarch-sdks

License

MIT