🔦 Beacon

A NANDA City-of-Agents citizen that returns on-chain trust evidence. A witness, not a judge.

A vanilla agent in the city can't read Ethereum — no wallet, no RPC, no ABI. Beacon crosses that gap for it. Hand Beacon an agent and it resolves the agent through the NANDA registry first, then reads Ethereum's ERC-8004 Identity and Reputation registries on Base Sepolia, and returns trust evidence — not a verdict.

Beacon reports the receipts and leaves the trust decision to the caller and to NANDA.

Live deployment

Beacon is deployed and registered as a citizen in the NANDA City of Agents.

Service	https://nanda-beacon-production.up.railway.app
Agent card	https://nanda-beacon-production.up.railway.app/.well-known/agent.json
SKILL.MD	https://nanda-beacon-production.up.railway.app/SKILL.MD
City registry	agent_id: beacon — GET http://67.205.176.71/api/registry/lookup/beacon

Try it (reads real ERC-8004 data on Base Sepolia, live):

curl -s -X POST https://nanda-beacon-production.up.railway.app/chat \
  -H 'content-type: application/json' \
  -d '{"message":"enrich agent 17"}'

Or run the narrated end-to-end demo (no dependencies):

python3 demo.py            # hits the live deployment
python3 demo.py --pause    # step through it on a screen-share

Why

Trust on the agentic web is shifting from human oversight to protocol design. NANDA's registry gives agents discovery and identity (the Brief/Claim tiers in the Hu & Rong taxonomy). What it doesn't carry is the Reputation and Proof+Stake tiers — and those live on-chain in ERC-8004. Beacon is the bridge: it lets any city citizen consult that on-chain evidence without becoming a web3 developer. NANDA stays the front door; Beacon just adds the trust column.

Evidence tiers

Output maps to the inter-agent trust taxonomy of Hu & Rong, Inter-Agent Trust Models (AAAI 2026), over the NANDA Index (Raskar et al., 2025):

Tier	Source	What it shows
Brief	NANDA city registry (read first)	name, description, capabilities, tags
Claim	ERC-8004 Identity Registry tokenURI	on-chain AgentCard, supportedTrust, active
Reputation	ERC-8004 Reputation Registry	interaction count + aggregate summary
Proof+Stake	ERC-721 ownerOf at a block height	the controlling address (proof of control)

Run it

python3 -m venv .venv && source .venv/bin/activate
pip install -e ".[dev]"
cp .env.example .env

# offline (mock) — for tests and demo safety
CHAIN_MODE=mock pytest -q

# live — reads real Base Sepolia data
uvicorn beacon.main:app --host 0.0.0.0 --port 6000
curl -s localhost:6000/health
curl -s -X POST localhost:6000/chat -H 'content-type: application/json' \
  -d '{"message":"enrich agent 17"}' | python -m json.tool

Endpoints

Route	Purpose
GET /health	{"agent_id":"beacon","status":"ok"}
GET /.well-known/agent.json	the NANDA agent card
POST /chat	{"message": "..."} → evidence
POST /a2a	{"from": "...", "message": "..."} → evidence
GET /SKILL.MD	how a vanilla agent calls Beacon

Invariants

• Read-only. No private key exists anywhere in the service; eth_call only.
• NANDA first. The registry lookup always runs before any chain read.
• Witness, not judge. No verdict/decision field is ever emitted (enforced in tests).
• Deterministic decode of on-chain AgentCards.

License

MIT © 2026 James Carnley