xenarch 0.2.3

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 on-chain. 0% Xenarch fee. The agent wallet only ever holds USDC — no ETH, no gas coin needed.

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 on-chain. 0% Xenarch fee — no Xenarch contract in the money flow. The agent wallet only ever holds USDC — no ETH, no other gas coin needed.

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)
Agent needs ETH	n/a	n/a	✓ never
Fee	Platform rate	Platform rate	0% — no Xenarch contract that can charge a fee
Open standard	proprietary	proprietary	x402 + pay.json (open)

Settlement happens on-chain via the x402 standard. 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. Agent wallet only holds USDC; no ETH required.

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 on-chain, 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

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 on-chain as a direct USDC transfer from the agent's wallet to the publisher's wallet. Funds never touch Xenarch infrastructure — 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.

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