keptvow

Check who your AI agent is about to pay before an x402 payment goes out.

Every answer is one word — ok, careful or stop — with the reason, built from real USDC payments on Base (how many different buyers paid the seller, how many came back), reports from buyers who did or didn't get what they paid for, and daily checks that the seller's services answer. Free, no sign-up, no key, no dependencies.

pip install keptvow

Ask about one wallet

import keptvow

result = keptvow.check("0xSELLER", amount_usd=5)
result["verdict"]   # "ok", "careful" or "stop"
result["advice"]    # one plain sentence saying why

Guard every payment (one line)

On the official x402 client (x402Client or x402ClientSync from the x402 package):

import keptvow
from x402 import x402Client

client = keptvow.hooks(x402Client())   # then register your schemes as usual

The wallet each payment goes to is checked just before the payment is signed. A wallet with a bad record cancels the payment before any money moves (x402 raises PaymentAbortedError, with Keptvow's reason). The async client's check runs off the event loop. Takes the same options as guard below.

Check a seller's 402 answer before paying

Works with requests and httpx responses:

r = session.get(url)
if r.status_code == 402:
    keptvow.guard(r)   # raises keptvow.KeptvowStop for a wallet with a bad record
    # ...go on and pay with your x402 client

guard(r, allow_careful=False) also blocks wallets with no track record; fail_open=False blocks payment when Keptvow can't be reached.

Report whether you got what you paid for

keptvow.report_outcome(paid_response)          # reads the PAYMENT-RESPONSE receipt
keptvow.report_outcome("0xTX", delivered=False) # or name the payment yourself

Sent in the background and never raises. Keptvow checks the payment on-chain, so only real buyers count — this is what lets honest sellers earn ok and flags the ones that take the money and deliver nothing.

Set KEPTVOW_URL to use another Keptvow address.

Other ways in

No package needed: GET https://keptvow.com/v1/check?pay_to=0x…&amount_usd=5, an MCP server at https://keptvow.com/mcp, and a guide for AI agents at https://keptvow.com/llms.txt. Everything else: https://keptvow.com/docs.