x402 Counterparty Score

Decision-grade counterparty scores for the x402 ecosystem, sold to AI agents over MCP (Model Context Protocol) with per-call x402 payments (USDC). Input an x402 endpoint URL or pay-to address; output is a trust verdict (trusted/caution/avoid) with wash-trading ratio, real-buyer count, and repeat-buyer rate. Every response carries provenance: source, updated_at, confidence.

Live on Base mainnet since 2026-07-10. The only settlement so far is our own, and it is on-chain and checkable: 0x9b29f10ffd9ac21136da31fa0780cdbed5ade48d2e58028bcb60ca4ab4b66b97 — $0.02 USDC on Base. Read it for what it is: the disclosed bootstrap settlement, a self-purchase from a wallet we control, published under five disciplines before it executed. It is not a customer sale, it is never counted as one, and it is never repeated. Full disclosure on the methodology page.

This page exists for humans verifying the service before funding an agent wallet. Agents consume the service directly over MCP; the machine-readable descriptions below are the exact tool contract.

Try it live

The free teaser tool runs from this page: the button below opens an MCP session against POST /mcp on this origin and calls get_sample_score, then prints the server's raw JSON-RPC result. No payment and no account. What leaves your browser is the MCP request itself: it is recorded like any other free-tool call, and nothing about you is collected.

The same requests by hand — this is the whole protocol, and it is what the button does:

curl -isS -X POST https://x402score.org/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"curl","version":"0.0.0"}}}'
# take the mcp-session-id response header, then:
curl -sS -X POST https://x402score.org/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -H 'mcp-session-id: SESSION_ID' \
  -d '{"jsonrpc":"2.0","method":"notifications/initialized"}'
curl -sS -X POST https://x402score.org/mcp \
  -H 'content-type: application/json' \
  -H 'accept: application/json, text/event-stream' \
  -H 'mcp-session-id: SESSION_ID' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"get_sample_score","arguments":{}}}'
# done — close the session (the server advertises DELETE in its 405 Allow header)
curl -sS -X DELETE https://x402score.org/mcp \
  -H 'accept: application/json, text/event-stream' \
  -H 'mcp-session-id: SESSION_ID'

Tools

Tool	Price	Description (verbatim tool contract)
`score_x402_counterparty`	$0.02/call	Returns trust verdict (trusted/caution/avoid) with wash-trading ratio, real-buyer count, and repeat-buyer rate for an x402 endpoint URL or pay-to address. $0.02/call. Computed from Base on-chain settlement data and the x402 Bazaar catalog; a score is sold only if refreshed within the past 24 hours.
`get_sample_score`	Free	Returns a clearly-marked stale sample counterparty score in the exact response schema of score_x402_counterparty (verdict, wash_trading_ratio, real_buyer_count, repeat_buyer_rate, source, updated_at, confidence). Free, no payment required, no input required. Sample data is fixed and expired by design — use it to validate response parsing, then call score_x402_counterparty ($0.02/call) for fresh decision-grade scores.

Connect an MCP client

Three steps to reach the free tool from a client you already run. The endpoint speaks MCP Streamable HTTP: https://x402score.org/mcp.

Point an MCP client at that URL over the HTTP transport. Two that need no setup: the official MCP Inspector, npx @modelcontextprotocol/inspector, which connects from a local browser UI; or Claude Code, claude mcp add --transport http x402score https://x402score.org/mcp.
Let the client run the initialize handshake. It returns server info and a mcp-session-id header that the following requests carry.
Call get_sample_score with no arguments. It is free and returns the exact response schema of the paid tool, with the sample flagged stale.

The paid tool needs more than an MCP client, and ordinary clients do not have it: an unpaid call returns a 402 quote, and settling that quote takes an x402-capable client (an agent runtime or SDK that implements the x402 payment flow) holding USDC on Base mainnet in a wallet it can sign with. MCP Inspector and Claude Code do not pay x402 quotes, so from those two the free tool is where a human stops — which is what the free tool is for: checking the schema and the service before an agent wallet is funded.

Endpoint and payment

MCP endpoint: send JSON-RPC 2.0 messages via POST /mcp on this origin (MCP Streamable HTTP). GET /mcp returns 405: the optional SSE notification stream is not offered.

Payment is per call via the x402 protocol in USDC. A call to the paid tool without payment returns an in-band quote; the quote is authoritative for price, asset, network, and pay-to address. Error responses settle no payment: stale or missing answers are never sold (answers older than 24 hours are withheld, not served).

Data sources

x402 Bazaar catalog — the official public discovery layer, read without a key.
Public on-chain settlement transfers, read via the CDP SQL API.
402 handshake probes of catalogued endpoints on each refresh — availability and declared price/schema, over the public x402 protocol.

Open, publicly licensed sources only; no commercial API data is resold. Per-source licensing basis is documented on the methodology page.

Verify this service

Methodology — deterministic scoring rules, verdict thresholds, confidence definition, coverage limits, probing and bootstrap-settlement disclosures.
OpenAPI specification — endpoint and tool input/output schemas, x402 payment flow, error envelopes.
llms.txt — the same facts, plain text.
Call get_sample_score over MCP — free, returns the exact response schema with a clearly-marked stale sample.