x402 Trust

x402-trust-mcp

An MCP server for discovering x402 endpoints and checking their trust before paying them: semantic and keyword search across the monitored catalog, plus trust scores, history, bulk scoring, and watches for any endpoint.

Backed by x402-trust.com, which monitors the x402 ecosystem on Base and Solana 24/7: uptime probes, 402-envelope spec compliance, price history, and real on-chain USDC settlement volume per endpoint. Every score is computed deterministically, no LLM involved, so the breakdown is fully auditable.

Tools

Tool	Cost	Description
x402_ecosystem_stats	free	Snapshot of the whole x402 ecosystem: endpoint counts, reachability, and real USDC settlement volume over 30 days.
x402_trust_leaderboard	free	Top-100 ranking of the most trustworthy x402 hosts, scored by their whole measured surface. Page with offset.
x402_verified_providers	free	Hosts that proved domain control and confirmed a contact email. Informational only, verification never changes the score.
x402_search	free	Substring search over host, URL and service name across the catalog.
x402_semantic_search	free	Meaning-based search: describe the capability you need in plain words. Discovery only, no verdicts.
x402_trust_preview	free	Three complete trust reports (best, median, worst) exactly as x402_trust_score returns them.
x402_trust_score	paid	The full trust verdict for one endpoint: score 0-100, grade, recommendation, price, and flags. Unknown endpoints get live-probed on the spot.
x402_endpoint_history	paid	Raw probe and event history for one endpoint over 1-90 days.
x402_find_alternatives	paid	Semantically similar endpoints that out-score a given one. Empty result means nothing beats it.
x402_trust_bulk	paid	Score up to 500 endpoints in one call; the cheapest fitting tier (10/50/100/200/500) is picked automatically.
x402_watch_create	paid	30-day monitor for one endpoint: alerts on payTo or price changes, delisting, spec regressions and downtime, via polling or webhooks. Returns a one-time secret.
x402_watch_events	free	Poll a watch's event log with watch id and secret, paging by the returned cursors.
x402_watch_edit	free	Change a watch's webhook URLs, sensitivity or subscribed events.
x402_watch_cancel	free	Stop a watch now; its log stays readable until expiry.
x402_watch_renew	paid	Add another 30 days to an active watch. Same secret.

Paid tools cost from $0.005 (single lookup) to ~$0.50 (500-endpoint bulk), charged over x402 (USDC on Base). With X402_PRIVATE_KEY set the server auto-pays within your limits; otherwise it returns the price quote for your host to pay. List tools page with limit (max 25) + offset and return a total.

Field-level documentation, verdict semantics, watch cursor rules and webhook signature details live at x402-trust.com/llms.txt; every response is self-describing via its schema at x402-trust.com/schemas.

Install

Add to your MCP client config (e.g. Claude Desktop claude_desktop_config.json):

{
  "mcpServers": {
    "x402-trust": {
      "command": "npx",
      "args": ["-y", "x402-trust-mcp"]
    }
  }
}

To enable autonomous payment for the paid tools, add a funded Base USDC wallet:

{
  "mcpServers": {
    "x402-trust": {
      "command": "npx",
      "args": ["-y", "x402-trust-mcp"],
      "env": {
        "X402_PRIVATE_KEY": "0xYOUR_BASE_WALLET_KEY",
        "X402_MAX_USD": "0.05"
      }
    }
  }
}

Configuration (env vars)

Var	Default	Description
X402_TRUST_API_BASE	https://x402-trust.com	API base URL.
X402_PRIVATE_KEY	(unset)	Base wallet private key. Enables auto-pay for paid tools. A set-but-malformed key logs a warning and leaves auto-pay off.
X402_MAX_USD	0.05	Per-call auto-pay ceiling. 0 disables auto-pay.
X402_MAX_TOTAL_USD	1.00	Cumulative auto-pay cap per process. 0 = unlimited.
X402_MAX_CALLS	1000	Max paid calls per process. 0 = unlimited.
X402_TIMEOUT_MS	20000	Request timeout.
X402_BASE_RPC_URL	public Base RPCs	Endpoint for the pre-signing USDC balance check (free eth_call; defaults to the public Base mainnet/Sepolia RPCs).

The free tools work with no configuration at all.

Security

X402_PRIVATE_KEY is a hot wallet: fund it with only what you are willing to spend on trust lookups. The key never leaves your machine; it signs EIP-3009 payment authorizations locally, after policy checks: chain allow-list (Base mainnet by default), canonical USDC contract verification, and the spend and call-count caps above. Before every payment the client re-reads the wallet's USDC balance: a wallet that cannot cover the quote is refused locally, before anything is signed, so an empty wallet never produces failed settlement attempts, and a top-up takes effect on the very next call.

Response signatures

Signed tool results carry a top-level signature block: an Ed25519 signature over the JCS-canonicalized (RFC 8785) response. It proves the content was assembled by x402-trust and not modified afterwards.

One rule matters when verifying: pin the trust anchor, never follow it from the response. signature.publicKeys is a discovery hint; a forged response would point at the attacker's own key document and still verify. Pin the public key itself or fetch https://x402-trust.com/.well-known/x402-trust-keys.json once at bootstrap and cache it. A worked test vector and a 20-line reference verifier live at x402-trust.com/schemas. Watch management responses are unsigned by design: they carry capability secrets that must never be forwarded as evidence.

License

MIT