Here's a pattern I kept hitting while running a small fleet of agents:
Agent A needs market data. It finds a paid API, checks that the endpoint is alive, checks the price, makes the call. Twenty minutes later Agent B needs market data. It finds the same API… and checks that the endpoint is alive, checks the price. Same check, same result, new tokens, new latency, new cost. Multiply by every agent, every task, every session — because agents start cold, they re-derive trust from scratch every single time.
Humans solved this ages ago. We don't personally re-audit a CA certificate on every HTTPS request; we verify a signature over someone else's audit. Agents have no equivalent. Every agent is its own tiny, wasteful certificate authority.
The fix I landed on: stop treating verification as something each agent does, and start treating it as something an agent can hold — a signed,portable, reusable object.
Concretely: my node continuously probes the paid (x402) agent services my agents actually use — a real HTTP 402 challenge every 10 minutes, recording liveness, latency, and the quoted price. Each probe is published as an attestation:
{
"payload": {
"type": "erabi.x402.probe/0.1",
"slug": "exa-search",
"ts": "{{ts}}",
"alive": true,
"http_status": 402,
"latency_ms": {{latency}},
"price_usd": {{price}},
"window_24h": { "probes": {{probes}}, "uptime_pct": {{uptime}} }
},
"sig": "ed25519:…",
"key": "…"
}
The signature is a detached ed25519 over the canonicalized payload (RFC 8785), verifiable against the node's published key. An agent that wants to know "is this API worth paying?" fetches this, verifies one signature, and moves on. No probe, no burned call, no re-derived trust:
curl https://erabi-production.up.railway.app/index/v1/services/exa-search/attestation
The index currently covers 16 real pay-per-call services (search,
browser automation, market data, inference…). Some things the data
already surfaced:
Everything is public: the human view at
https://erabi-explorer.vercel.app/services , the agent view at
/index/v1/services
(JSON), and each service's attestation endpoint.
"Agents re-verify what other agents already verified" is not an x402
problem — it's everywhere. Test results, security scans, dependency
checks, doc freshness: agent fleets redundantly re-derive the same facts because there's no trusted medium of exchange for verification itself.
Signed attestations are that medium. Verify once, sign it, let everyone (and every agent) reuse it — and make the signer accountable for it.
The reliability index is my first concrete cut at this, built on an open intent-exchange protocol (Apache-2.0, https://github.com/HMAKT99/Erabi )
where identities are Ed25519 keypairs and outcomes are dual-signed on a public ledger. If your agents keep re-checking things other agents already checked, I'd genuinely like to hear what they re-check — that's the next thing the index should carry.