ERC-8004 agent trust scores, search, metadata, and identity lookups via x402 micropayments on Base.
What it does
The ERC-8004 Trust API ("The Oracle") by 8k4protocol is a read-only API that provides trust scores, metadata, search, and identity resolution for on-chain AI agents registered under the ERC-8004 standard. It supports agents across BSC, Base, and Ethereum chains. The `/metrics` endpoint specifically returns platform-level metrics and is gated behind an x402 payment of $0.01 per call, settled on Base (eip155:8453) via the Coinbase x402 facilitator.
The broader API surface includes numerous paid and free endpoints. Paid endpoints (each $0.001 unless noted) include agent trust score lookups (`/agents/{agent_id}/score`), score explanations with positives/cautions (`/agents/{agent_id}/score/explain`), agent validation histories, semantic agent search (`/agents/search`), agent cards, wallet-to-agent resolution, cross-chain identity lookups, and metadata nonce generation. Metadata upload costs $0.10 per call. The `/stats` endpoint costs $0.01. Free endpoints include `/health`, `/stats/public`, `/agents/top`, and public metadata retrieval. All paid endpoints use the x402 protocol with fixed pricing, paying to address `0xb273616670037C0870E9835B3FFBE68f58de68B0` on Base.
The API is documented via OpenAPI 3.1.0 (version 1.2.0) and uses API key authentication (via `X-API-Key` header) for non-paid endpoints, while paid endpoints accept x402 payment challenges. Response schemas are well-defined, including `ScorePublicResponse` with fields for score, score_tier, trust_tier, confidence level, and adjustment reasons.
Capabilities
Use cases
- —Look up the trust score and tier of an ERC-8004 registered AI agent before delegating a task
- —Search for agents capable of a specific task, filtered by minimum trust score and chain
- —Resolve a wallet address to its registered agents and their trust scores
- —Upload or retrieve on-chain metadata for an ERC-8004 agent
- —Audit an agent's validation history including on-chain feedback and ratings
Fit
Best for
- —AI agent orchestrators that need to evaluate agent trustworthiness before delegation
- —Multi-agent systems requiring on-chain reputation data across BSC, Base, and Ethereum
- —Developers building agent marketplaces or directories with trust-based ranking
Not for
- —General-purpose blockchain analytics unrelated to ERC-8004 agents
- —Applications needing sub-cent micropayments (minimum call cost is $0.001)
- —Off-chain agent reputation systems with no ERC-8004 registration
Quick start
# Get the trust score for agent 42 on BSC (requires x402 payment)
curl -X GET 'https://api.8k4protocol.com/agents/42/score?chain=bsc'
# Returns 402 with x402 challenge; pay and retry with payment header
# Free: get top agents
curl -X GET 'https://api.8k4protocol.com/agents/top?limit=5&chain=bsc'Example
Response
{
"as_of": "2025-01-15T12:00:00Z",
"chain": "bsc",
"score": 0.85,
"adjusted": false,
"agent_id": 42,
"global_id": "bsc:42",
"confidence": "medium",
"disclaimer": "Scores are informational only.",
"score_tier": "high",
"trust_tier": "trusted",
"score_version": 2,
"adjustment_reasons": [],
"validator_count_bucket": "10-50"
}Endpoint
Quality
Full OpenAPI 3.1.0 schema with well-defined request/response models, clear x402 pricing on all paid endpoints, and a live 402 challenge captured on /metrics. Docs link exists but external docs page was not crawled, and no usage examples are provided in the spec itself. Response example is inferred from schema.
Warnings
- —External documentation at https://8k4protocol.com/docs/ was not crawled; details may differ from OpenAPI spec
- —The /metrics endpoint is not explicitly listed in the OpenAPI spec paths, though it returns a valid x402 challenge
- —Response example for ScorePublicResponse is inferred from schema field names and types, not from an actual API response
Citations
- —The API is titled 'ERC-8004 Trust API' version 1.2.0 described as 'The Oracle - Read-only API for agent trust scores'https://api.8k4protocol.com
- —The /metrics endpoint returns a 402 challenge with price $0.01 on Base (eip155:8453)https://api.8k4protocol.com/metrics
- —Paid endpoints pay to 0xb273616670037C0870E9835B3FFBE68f58de68B0 via Coinbase x402 facilitatorhttps://api.8k4protocol.com
- —Agent search endpoint costs $0.001 per call with x402 fixed pricinghttps://api.8k4protocol.com
- —Metadata upload costs $0.10 per callhttps://api.8k4protocol.com
- —Supports chains: bsc, base, ethhttps://api.8k4protocol.com