ERC-8004 agent trust scores, metadata, and search — pay-per-call via x402 on Base
What it does
The 8k4 Protocol API ("The Oracle") is a read-only trust-scoring service for ERC-8004 registered AI agents. It exposes endpoints to look up agent metadata, compute and explain trust scores, search for agents by task, retrieve on-chain validation feedback, and list top-ranked agents. The API supports agents registered on BSC, Base, and Ethereum chains.
Several endpoints are gated behind x402 micropayments settled on Base (eip155:8453) via the Coinbase CDP facilitator. Paid endpoints include agent score lookup, score explanation, agent search, agent card, wallet score, wallet agents, identity registrations, validations, and full stats — each priced at $0.001 per call except metadata upload ($0.10) and full stats ($0.01). Free/open endpoints include the metadata JSON reader, top agents leaderboard, public stats, and health check. API key authentication (X-API-Key header) is used for non-paid endpoints that still require identification.
The OpenAPI 3.1.0 spec is comprehensive, covering 20+ routes with well-defined request/response schemas including ScorePublicResponse, ScoreExplainResponse, MetadataResponse, TopAgentResponse, FeedbackItem, and StatsResponse. The specific endpoint listed here — `/agents/21480/metadata.json` — is an open (no payment required) GET endpoint that returns the metadata object for agent ID 21480. The probe returned 404 on GET, which likely means agent 21480 does not exist or has no metadata stored, rather than indicating the endpoint itself is broken.
Capabilities
Use cases
- —Look up the trust score and tier of an ERC-8004 registered AI agent before delegating a task
- —Search for capable agents by task description, filtering by minimum trust score or reachability
- —Retrieve on-chain validation feedback and ratings left by validators for a specific agent
- —Upload or update agent metadata with a signed payload, paying $0.10 per upload via x402
- —Resolve a global agent identity across BSC, Base, and Ethereum chains
Fit
Best for
- —AI agent orchestrators that need to vet agents before delegation
- —Multi-agent systems requiring trust-based agent selection
- —Developers building on the ERC-8004 agent registry standard
- —Wallets or dashboards displaying agent reputation data
Not for
- —General-purpose web search or non-agent data lookups
- —Use cases requiring free unlimited access — most endpoints are paid
- —Agents not registered under the ERC-8004 standard
Quick start
curl https://api.8k4protocol.com/agents/1/metadata.json?chain=bscExample
Response
{
"chain": "bsc",
"agent_id": 1,
"metadata": {
"name": "ExampleAgent",
"description": "An ERC-8004 registered agent",
"capabilities": [
"data-analysis"
]
}
}Endpoint
Quality
Full OpenAPI 3.1.0 spec with detailed schemas and clear x-payment-info annotations. However, the specific listed endpoint (/agents/21480/metadata.json) returned 404 on GET, suggesting agent 21480 doesn't exist. No external documentation was reachable beyond the API root JSON. Pricing is clearly documented in the spec.
Warnings
- —The specific endpoint /agents/21480/metadata.json returned 404 on GET — agent 21480 may not exist or have metadata stored
- —No external documentation site (8k4protocol.com/docs/) was crawled to verify claims
- —The listed endpoint is an open/free metadata reader; the broader API has paid x402 endpoints
Citations
- —API self-describes as 'ERC-8004 Trust API — The Oracle — Read-only API for agent trust scores' version 1.2.0https://api.8k4protocol.com
- —Paid endpoints use x402 on Base (eip155:8453) with Coinbase CDP facilitator at prices from $0.001 to $0.10https://api.8k4protocol.com
- —Supports chains: bsc, base, ethhttps://api.8k4protocol.com
- —Root returns service status ok with docs link to https://8k4protocol.com/docs/https://api.8k4protocol.com