OTR Protocol

The merchant trust layer for AI agent commerce
Deterministic, verifiable, open-source merchant trust scoring for the agentic economy
Protocol v4.1

Specification • Scoring Algorithm • Quick Start • Packages • Contributing

The Problem

AI agents are increasingly making purchase decisions on behalf of consumers. The agentic commerce stack is taking shape -- but there is a critical missing layer:

Code

┌──────────────────────────────────────────────────────────────────┐
│                  AI Agent Commerce Protocol Stack                 │
├──────────────────────────────────────────────────────────────────┤
│                                                                   │
│   Visa TAP ·············· Agent Identity Verification             │
│   Google UCP ············ Structured Data Exchange                 │
│   Stripe ACP ············ Payment Processing                      │
│                                                                   │
│   ┌───────────────────────────────────────────────────────────┐   │
│   │  OTR Protocol ·····  MERCHANT TRUST VERIFICATION  ◀━━━━━ │   │
│   │                      "Is this merchant safe to buy from?" │   │
│   └───────────────────────────────────────────────────────────┘   │
│                                                                   │
│   Visa TAP answers "Who is the AI agent?"                         │
│   Google UCP answers "What products are available?"               │
│   Stripe ACP answers "How do I pay?"                              │
│   OTR answers "Should I trust this merchant?"  ◀━━ ONLY OTR      │
│                                                                   │
└──────────────────────────────────────────────────────────────────┘

Without OTR, AI agents operate blind -- unable to distinguish a legitimate retailer from a sophisticated scam site. This exposes consumers to fraud and erodes trust in the entire agentic commerce ecosystem.

The Solution

OTR (Open Trust Registry) provides deterministic, verifiable merchant trust scores using 6 verification dimensions, a 10-layer anti-fraud pipeline (Layer 0: Google Web Risk one-vote veto + Layers 1-9: core detection engine), and three-layer immutable audit trail. It is fully open-source (MIT), machine-readable, and designed from the ground up for AI agent consumption.

Key Properties

Deterministic -- Same inputs always produce identical outputs. Any validator can reproduce any score.
Verifiable -- All data sources are publicly accessible. No hidden factors or proprietary signals.
Unforgeable -- Verification dimension weighted at 40% in public assessment. SEC filings, Wikidata entries, and 10-year domain age cannot be faked.
Tamper-proof -- SHA-256 hash chain + Base L2 blockchain anchoring + IPFS monthly snapshots.
Fair -- No pay-for-trust. Scores reflect behavior, not subscription level.
Category-aware -- Three site categories (ecommerce / saas / non_commerce) with tailored scoring weights.
Safety-first -- Google Web Risk Layer 0 one-vote veto: flagged domains get score=0, status SUSPENDED.

Quick Start

bash

# Verify any merchant instantly
npx @otr-protocol/validator verify nike.com

# Output:
# ┌──────────────────────────────────────────────┐
# │  nike.com                             GOLD   │
# │  Trust Score: 88/100   Category: ecommerce   │
# │  OTR-ID: OTR-1C-7F3A2B9E4D1C-K4             │
# │                                              │
# │  Verification:   85  ██████████████░░        │
# │  Security:       80  █████████████░░░        │
# │  Governance:     72  ████████████░░░░        │
# │  Transparency:   75  ████████████░░░░        │
# │  Data Quality:   65  ██████████░░░░░░        │
# │  Fulfillment:    --  (COLD mode)             │
# └──────────────────────────────────────────────┘

For AI Agents (MCP Server)

The OTR MCP Server uses the standard Model Context Protocol and works with all MCP-compatible clients.

Claude Desktop / Claude Code -- add to claude_desktop_config.json:

config.json

{
  "mcpServers": {
    "otr": {
      "command": "npx",
      "args": ["@otr-protocol/mcp-server"]
    }
  }
}

Cursor / Windsurf / Cline -- same configuration in .cursor/mcp.json or equivalent. Any client implementing the MCP specification works out of the box.

Now any AI agent can verify merchants in natural language:

"Is nike.com trustworthy?" --> OTR returns trust score 88/100, badge GOLD, and a 6-dimension breakdown (Verification, Security, Governance, Transparency, DataQuality, Fulfillment) with evidence sources.

Two MCP Tools — One Call = Complete Answer

Tool	Description	Returns
`verify_merchant`	Complete merchant profile in one call	Trust score (0-100), badge, 6-dimension breakdown, safety status (Google Web Risk), site classification (ecommerce/saas/non_commerce), entity data, policy URLs, data sources
`search_registry`	Search the OTR merchant registry	Paginated merchant list with scores, badges, and recommendations

Design philosophy: AI agents should get everything they need in a single tool call. verify_merchant returns trust assessment + purchase capabilities + links + policy URLs + data freshness — no need to chain multiple calls.

TypeScript SDK

server.ts

import { OtrClient } from "@otr-protocol/sdk";

const otr = new OtrClient();
const result = await otr.verify("nike.com");

console.log(result.trustScore);   // 88
console.log(result.badge);        // "GOLD"
console.log(result.dimensions);   // { verification: 85, security: 80, ... }

// Search the registry
const results = await otr.search("electronics", { minScore: 70 });

Core Scoring Engine

server.ts

import { calculateTrustScore } from "@otr-protocol/core";

// Deterministic: same inputs always produce identical outputs
const result = calculateTrustScore({
  hasSecFiling: true,
  hasStockSymbol: true,
  stockExchange: "NYSE",
  hasWikidataId: true,
  trancoRank: 500,
  domainAgeYears: 15,
  // ... 40+ evidence fields
});

console.log(result.trustScore);  // 88
console.log(result.badge);       // "GOLD"
console.log(result.tier);        // "TIER_4"

Architecture

Code

                         ┌─────────────────────────────────┐
                         │       AI Agent / Application      │
                         │   "Should I buy from example.com?" │
                         └──────────────┬──────────────────┘
                                        │
                    ┌───────────────────┼───────────────────┐
                    │                   │                    │
              ┌─────▼─────┐     ┌──────▼──────┐    ┌──────▼──────┐
              │ MCP Server │     │  REST API   │    │   SDK       │
              │  (stdio)   │     │  /api/otr   │    │  npm pkg    │
              └─────┬──────┘     └──────┬──────┘    └──────┬──────┘
                    │                   │                    │
                    └───────────────────┼───────────────────┘
                                        │
                         ┌──────────────▼──────────────┐
                         │      OTR Scoring Engine       │
                         │   @otr-protocol/core          │
                         │                               │
                         │  ┌─────────────────────────┐  │
                         │  │ 6 Dimension Evaluators   │  │
                         │  │ Verification | Security  │  │
                         │  │ Governance | Transparency│  │
                         │  │ DataQuality | Fulfillment│  │
                         │  └─────────────────────────┘  │
                         │  ┌─────────────────────────┐  │
                         │  │ 10-Layer Anti-Fraud      │  │
                         │  │ Domain Age | SSL | DNS   │  │
                         │  │ Pattern | Tranco | ...   │  │
                         │  └─────────────────────────┘  │
                         │  ┌─────────────────────────┐  │
                         │  │ Brand Fast-Track         │  │
                         │  │ SEC + Tranco + Wikidata  │  │
                         │  └─────────────────────────┘  │
                         └──────────────┬──────────────┘
                                        │
              ┌─────────────────────────┼─────────────────────────┐
              │                         │                          │
     ┌────────▼────────┐    ┌──────────▼──────────┐    ┌─────────▼─────────┐
     │  Public Data     │    │  Merchant Bridge     │    │  Immutable Audit   │
     │  Sources         │    │  (Verified Only)     │    │  Trail             │
     │                  │    │                      │    │                    │
     │  SEC EDGAR       │    │  Product Catalog     │    │  SHA-256 Hash      │
     │  Wikidata        │    │  Order Data (agg)    │    │  Chain             │
     │  Tranco List     │    │  Delivery Metrics    │    │  Base L2 Anchoring │
     │  DNS Records     │    │  Tracking Numbers    │    │  IPFS Snapshots    │
     │  SSL Certs       │    │  (desensitized)      │    │                    │
     │  Finnhub.io      │    │                      │    │                    │
     │  Google Web Risk │    │                      │    │                    │
     │  Website Scan    │    │                      │    │                    │
     └─────────────────┘    └──────────────────────┘    └───────────────────┘

How Scoring Works

6 Trust Dimensions

Weights vary by site category:

#	Dimension	E-Commerce COLD	SaaS COLD	AUTH Mode	What It Measures
1	Verification	0.40	0.37	0.10	Stock exchange, Wikidata, GLEIF LEI, domain age, Tranco rank, payment processors
2	Security	0.15	0.20	0.10	SSL/TLS, DMARC, SPF, DKIM, HSTS, DNSSEC, CSP, CAA, WAF, security.txt (15 signals)
3	Governance	0.20	0.23	0.10	Privacy policy, GDPR/CCPA, terms, refund/return, shipping, cookie consent (10 signals)
4	Transparency	0.10	0.15	0.05	robots.txt, sitemap, Schema.org, hreflang, AI crawler policy, llms.txt, about page
5	Data Quality	0.15	0.05	0.25	E-commerce: 22 product data signals. SaaS: 12 platform signals (API docs, SLA, pricing, security certs)
6	Fulfillment	--	--	0.40	Delivery speed, return window, tracking, shipping policy (COLD mode: not scored)

What Each Dimension Measures

Dimension	Evaluates
Verification (V)	Is this a real, registered business? SSL certificate type, GLEIF LEI, Wikidata entity, SEC filings, domain age, payment processor detection
Security (S)	Is the site technically secure? DMARC, SPF, DKIM, HSTS, CSP, WAF, DNSSEC configuration
Governance (G)	Does it follow business rules? Privacy policy, refund policy, shipping policy, cookie consent, regulatory compliance
Transparency (T)	Is it machine-readable? robots.txt, Schema.org structured data, llms.txt, protocol endpoint availability
Data Quality (D)	Is product/service data complete? Product count, image coverage, price format consistency, category taxonomy depth
Fulfillment (F)	Does it deliver on promises? Order completion rate, delivery time, return rate, dispute rate (AUTH mode only — requires merchant data)

Why Weights Differ by Category

E-commerce: Verification weighted highest (0.40) because buyers need to trust the store before purchasing. Identity signals (SEC filings, Wikidata, domain age) are the strongest defense against fraudulent shops.
SaaS: Security (0.20) and Governance (0.23) weighted higher because SaaS platforms handle user data and need clear policies. Users entrust ongoing access to their information.
Non-commerce: Not scored. Sites that do not sell products or services lack applicable commerce dimensions (product data, checkout, fulfillment).

Three Site Categories

Category	Description	Scoring
`ecommerce`	Online stores selling physical/digital products	Full 6-dimension scoring with product D signals
`saas`	Software-as-a-Service platforms	Tailored weights (V=37%, G=23%) with 12 SaaS D signals
`non_commerce`	Non-commercial sites (Wikipedia, government, etc.)	Not scored -- returns identity signals only

Non-Commerce Sites

Sites classified as non_commerce (e.g., Wikipedia, government portals, news sites) are not scored:

trustScore: null
badge: null
scanStatus: "non_commerce"
Basic verification data (SSL, entity info) is still returned, but no numerical trust score is assigned.

Reason: Non-commerce sites do not sell products or services, so trust scoring dimensions (product data, checkout, fulfillment) do not apply.

OTR-ID

Unique identifier assigned to each evaluated domain.

Format: OTR-1{mode}-{fingerprint}-{checksum}

1 — Protocol version
mode — C (COLD: pre-authorization scan) or A (AUTH: merchant authorized)
fingerprint — 12 uppercase hex chars, derived from SHA-256 of the normalized domain (first 48 bits)
checksum — 2 Base36 chars (Luhn mod-36 validation + deterministic salt)

Code

Example: OTR-1C-7F3A2B9E4D1C-K4

Properties:

Deterministic: Same domain always produces the same fingerprint
Irreversible: SHA-256 is cryptographically one-way; truncated to 48 bits, the original domain cannot be recovered
Collision-resistant: ~281 trillion possible fingerprints (2^48)

Lifecycle:

Event	Result	Status
First scan	OTR-1C generated	ACTIVE
Merchant authorizes	Upgraded to OTR-1A (same fingerprint, recalculated checksum)	UPGRADED
Domain identity change detected	OTR-ID revoked (set to NULL), domain re-enters cold-start	REVOKED
Google Web Risk flags domain	Score forced to 0	SUSPENDED
Anti-gaming multiplier < 0.10	Score forced to 0	SUSPENDED

Identity change is detected when weighted signals exceed threshold 3: GLEIF entity mismatch (3), nameserver change (2), content similarity < 30% (2), Wikidata P856 mismatch (2), domain parking > 90 days (2), SSL organization change (1).

Google Web Risk (Layer 0 Safety)

Google Web Risk operates as a Layer 0 one-vote veto, separate from dimension scoring:

Flagged domain → trustScore = 0, otrIdStatus = SUSPENDED, safety.googleWebRisk = true
Does not participate in dimension weight calculation
Overrides all other signals regardless of their values

Two Scoring Modes

Code

COLD Mode: Public Assessment (no merchant cooperation needed)
═══════════════════════════════════════════════════════════════
  E-Commerce: V (0.40) + S (0.15) + G (0.20) + T (0.10) + D (0.15) = Score
  SaaS:       V (0.37) + S (0.20) + G (0.23) + T (0.15) + D (0.05) = Score

  Nike (ecommerce):   V=85×0.40 + S=80×0.15 + G=72×0.20 + ...  = 83 GOLD
  Scam site:          V=10×0.40 + S=100×0.15 + G=90×0.20 + ...  = 39 UNRATED
                                                                    ↑ can't game Verification


AUTH Mode: Verified Merchant (merchant provides API access)
═══════════════════════════════════════════════════════════════
  F (0.40) + D (0.25) + V (0.10) + S (0.10) + G (0.10) + T (0.05) = Score

  Good merchant:   F=90×0.40 + D=85×0.25 + ...  = 78 SILVER
  Bad merchant:    F=30×0.40 + D=40×0.25 + ...  = 38 UNRATED
                                                    ↑ bad fulfillment = low score

Trust Badges

Badge	Score	AI Agent Action
PLATINUM	90-100	Safe to recommend with high confidence
GOLD	80-89	Strong trust, recommended for AI agents
SILVER	70-79	Recommend with standard caution
BRONZE	60-69	Display only, suggest user verify independently
UNRATED	0-59	Warn user about insufficient trust data

Scores 95+ trigger human review recommendation. No hard cap. If safety.status is "DANGEROUS" (Google Web Risk), DO NOT recommend regardless of score.

10-Layer Anti-Fraud Engine

OTR prevents fraudulent sites from gaming the system through a 10-layer detection pipeline:

Code

Layer 0  Safety Check        Google Web Risk API — malware/phishing one-vote-veto (instant block)
Layer 1  Domain Age          Certificate history analysis (crt.sh)
Layer 2  SSL Security        HTTPS/HSTS verification, self-signed detection
Layer 3  DNS Security        DMARC, SPF, DKIM policy completeness
Layer 4  Domain Pattern      Brand impersonation (amaz0n-deals.xyz), suspicious TLDs
Layer 5  Tranco Rank         Independent traffic ranking verification
Layer 6  Content Analysis    Phishing keywords, parked domains, empty pages
Layer 7  Redirect Chain      Cross-domain redirect detection
Layer 8  Cross-Signal        Multi-signal correlation and accumulation rules
Layer 9  Anti-Gaming         Signal-brand mismatch, identity-gameable gap, template suspect
         ▼
         Layer 0 DANGEROUS = immediate rejection (one-vote-veto)
         Single CRITICAL signal = immediate rejection
         Fraud score > 30 = rejection
         Anti-gaming multiplier applied to gameable dimensions

Anti-Gaming Detection Patterns (Layer 9)

Pattern	Trigger	Multiplier
Signal-Brand Mismatch	Gameable avg ≥ 80 + no Tranco/Wikidata/SEC + Identity < 30	0.5x
Identity-Gameable Gap	Identity < 20 + gameable avg > 70 + no established identity	0.7x
Template Site Suspect	Domain < 1yr + no Tranco/Wikidata/SEC + gameable avg > 60	0.5x
Domain Age Gate (<6mo)	Domain under 6 months	Cap at 50
Domain Age Gate (<1yr)	Domain under 1 year	Cap at 75

Anti-Gaming in Practice

Scenario	Old v3 Score	New v4 Score	Change
Nike (legitimate brand)	83 GOLD	83 GOLD	--
Scam site (perfect tech)	39 UNRATED	35 UNRATED	-4
Scam site + anti-gaming	28 UNRATED	22 UNRATED	-6

Data Integrity

OTR uses a three-layer immutable audit trail to ensure that historical scores cannot be tampered with:

Code

Layer 1: PostgreSQL Hash Chain (real-time, $0/year)
├── Every score change records SHA-256 hash
├── Each record links to previous via prev_hash
├── Any modification breaks the chain → detectable
└── verifyChainIntegrity() → instant verification

Layer 2: Base L2 Blockchain Anchoring (daily, ~$0.37/year)
├── Daily chain-head hash written to Base L2 smart contract
├── Externally verifiable by anyone
├── AWS KMS hardware security for signing keys
└── Transaction hash stored in otr_l2_anchors table

Layer 3: IPFS Monthly Snapshots (monthly, $0/year via web3.storage)
├── Full registry exported as content-addressed JSON
├── CID (Content Identifier) is immutable
├── Anyone can retrieve and verify the snapshot
└── CIDs recorded in otr_snapshots table

Public Verification Endpoints:

Code

GET /api/otr/audit/chain-integrity     Verify hash chain completeness
GET /api/otr/verify/:domain/history    Score history with trend data
GET /api/otr/audit/l2-anchors          Base L2 anchoring records
GET /api/otr/audit/snapshots           IPFS snapshot CID listing

Multi-Source Consensus

OTR never blindly trusts any single data source. Every external data point must pass cross-validation:

Code

Source Weights (not all sources are equally trustworthy):
  google-web-risk   1.0   Google Safe Browsing → one-vote-veto on DANGEROUS
  sec.gov           1.0   Government source → highest trust
  dns-query         0.9   Infrastructure → high trust
  tranco-list.eu    0.9   Academic source → high trust
  wikidata.org      0.8   Community source → high but editable
  finnhub.io        0.7   Commercial API → moderate-high trust
  website-scan      0.6   Self-reported → moderate trust
  product-sample    0.5   Product page sampling → public but limited scope
  merchant-api      0.4   Merchant-declared → low trust (can be faked)

Consensus Rules:
  ✓ 2+ sources agree → accepted (high confidence)
  ✗ Sources disagree → rejected (keep existing value)
  ⚠ Single source drift > 30% → anomaly flagged
  🔒 3+ anomalies from one source → auto-quarantine

Data Desensitization

When merchants provide fulfillment data, OTR applies 4 levels of privacy protection:

Level	Stage	What Happens
L1	Pre-transmission	Customer names → SHA-256 hash, addresses → country+city only, emails/phones/payments → deleted
L2	In transit	TLS 1.3 + HMAC-SHA256 signature + nonce anti-replay
L3	Server-side	Instant aggregation to statistics, raw data never persists
L4	Audit trail	Only metadata logged (timestamps, counts), never content

Why OTR?

Feature	OTR	Trustpilot	BBB	Google Merchant
AI-native API (MCP Server)	Yes	No	No	No
Deterministic scoring	Yes	No	No	No
Open-source algorithm (MIT)	Yes	No	No	No
No pay-for-trust	Yes	No	No	Yes
Multi-source verification	6 dimensions	1 (stars)	1 (grade)	Partial
Anti-gaming detection	10-layer	No	No	No
Machine-readable output	Full JSON	Partial	No	Partial
Immutable audit trail	3-layer	No	No	No
Category-aware scoring	3 types	No	No	No
Conformance test suite	Yes	N/A	N/A	N/A
Data desensitization	4-level	N/A	N/A	Partial

Packages

Package	Description	npm
`@otr-protocol/core`	Deterministic scoring engine -- the reference implementation
`@otr-protocol/mcp-server`	MCP Server for AI agents (Claude, Cursor, Windsurf, Cline)
`@otr-protocol/validator`	CLI tool for merchant verification
`@otr-protocol/sdk`	TypeScript client SDK for application integration

Conformance Testing

Any OTR implementation must pass the standard conformance test vectors:

Terminal

npm run conformance

The test suite validates determinism: identical inputs produce identical outputs across all implementations (TypeScript, Python, Go, Rust). This ensures a merchant's trust score is the same regardless of which validator computed it.

Test vectors in conformance/test-vectors.json cover:

Site category detection (ecommerce / saas / non_commerce)
Scoring mode detection (COLD vs AUTH)
Individual dimension scoring with category-specific weights
Badge and tier assignment (PLATINUM/GOLD/SILVER/BRONZE/UNRATED)
Anti-gaming detection and penalty application
Google Web Risk safety override
Non-commerce exclusion
Edge cases (empty data, null fields, boundary values)

Scoring Integrity

OTR Protocol maintains the integrity and independence of merchant trust scores through these commitments:

No Score Selling -- Trust scores cannot be purchased, sponsored, or commercially influenced. No premium tiers, sponsorships, or partnerships affect scoring.
No Pay-for-Trust -- Subscription status has zero impact on OTR scores. Free-tier merchants and enterprise customers are evaluated identically.
No Human Override -- All scores are computed algorithmically. No individual can manually adjust any score.
Algorithmic Transparency -- The entire algorithm is open-source (MIT). Anyone can audit, verify, and reproduce any score. Re-scanning the same domain produces the same score (deterministic pipeline).
Data-Driven Only -- Scores reflect independently verifiable signals. Merchant-submitted data is marked verified=false with scoringWeight=0 and requires corroboration from at least 2 independent authoritative sources.

Enforcement: Open-source code + conformance tests + governance process + 10-layer anti-gaming detection with compounding multipliers.

Mission

OTR exists to create a fair, transparent trust layer for the AI agent commerce era. Any merchant -- regardless of size or brand recognition -- can earn trust through verifiable performance. The only way to improve a score is to improve actual trust signals.

Public Data Sources

OTR evaluates merchants using publicly accessible data only (COLD mode). No merchant cooperation required.

Source	Data	Verifiable
DNS Records	SPF, DMARC, DKIM, DNSSEC, MTA-STS, CAA	Yes — standard DNS queries
SSL/TLS Certificates	Type (DV/OV/EV), issuing CA, organization	Yes — certificate transparency logs
HTTP Headers	HSTS, CSP, X-Frame-Options, Permissions-Policy	Yes — any HTTP client
Website Content	Policy pages, product catalog, Schema.org markup	Yes — public web pages
Tranco List	Domain popularity ranking (top 1M)	Yes — tranco-list.eu (academic)
WHOIS / crt.sh	Domain age, certificate history	Yes — public registries
Wikidata	Entity verification via P856 (official website)	Yes — wikidata.org (CC0)
GLEIF	Legal Entity Identifier (LEI), ISO 17442	Yes — gleif.org
SEC EDGAR	US regulatory filings	Yes — sec.gov
Finnhub / OpenFIGI	Stock exchange listings, ticker resolution	Yes — finnhub.io / openfigi.com
Google Web Risk	Malware, phishing, unwanted software detection	Yes — Google API

Roadmap

Phase	Status	Description
Phase 1	Complete	Open-source scoring engine, MCP Server, CLI, SDK, conformance tests
Phase 2	Complete	Hash chain integrity, L2 anchoring, IPFS snapshots, multi-source consensus, data desensitization, score decay, Google Web Risk Layer 0 safety, 3 site categories (ecommerce/saas/non_commerce), SaaS D-dimension 12 signals, COLD/AUTH scoring modes
Phase 3	Planned	IETF Internet-Draft standardization, Python/Go SDKs, academic paper

Contributing

We welcome contributions. See CONTRIBUTING.md for detailed guidelines.

Key requirements for scoring algorithm changes:

RFC-style proposal in spec/
Updated conformance test vectors
Determinism verification
Review by maintainers

License

MIT -- ORBEXA

Protocol Specification • Scoring Algorithm • Governance Model • Contributing Guide • Code of Conduct

_{Built by ORBEXA -- Infrastructure for Agentic Commerce}