Chain Overview

Who this is for: Engineers and architects building AI-agent-accessible payment stacks — evaluating protocol fit, validating card-network compliance, or wiring up A2A / x402 settlement.
What it produces: Seven §4 hash-anchored OpenChainGraph policy artifacts — a routing decision, branch-specific compliance assessments, and an MCP readiness mandate — that together form an auditable agentic-rail compliance bundle.
How to use it: Run ART-22 to determine your protocol path. If ART-22 recommends AP2/card networks, follow Branch A (ART-16 → ART-23 → ART-24). If it recommends A2A/x402, follow Branch B (ART-25 → ART-26 → ART-03). Finish with ART-18 regardless of branch. Export each §4 artifact; each child node can consume the parent's execution_hash in its chain.parent_hashes array.

ART-22 · Agentic Payments Protocol Comparator [ROOT · routing_policy]

│

├── Branch A: AP2 / Card Networks

│ ├── ART-16 · Google AP2 Mandate Builder [reuse]

│ ├── ART-23 · Visa Trusted Agent Protocol Inspector [new]

│ └── ART-24 · Mastercard Agentic Token Builder [new]

│

└── Branch B: A2A / x402

├── ART-25 · A2A Agent Card Validator [new]

├── ART-26 · x402 Payload Decoder [new]

└── ART-03 · x402 Settlement Modeler [reuse]

│

ART-18 · MCP Developer Readiness Scorecard [TERMINAL · reuse]

Root Node

⊙

ART-22 · routing_policy

Agentic Payments Protocol Comparator

Compare AP2, ACP, x402, Visa TAP, and Mastercard Agentic Token across 8 dimensions (backer, artifact, signing, scope, rail, identity, audit, status) and for 5 representative agentic scenarios. Determines whether your stack should follow Branch A (AP2/card networks) or Branch B (A2A/x402). Produces a routing_policy §4 artifact.

chain_depth: 0 parent_hashes: [] mandate_type: routing_policy T276 promoted

Open ART-22 →

Branch A — AP2 / Card Networks

Follow if ART-22 routes to Visa TAP or Mastercard Agent Pay

ART-16 · payment_mandate · Reused node

Google AP2 Mandate Builder

Builds a complete AP2 v0.2 Intent → Cart → Payment mandate chain for Google Pay + Gemini-agent flows. Verifies Intent, Cart, and Payment mandate linkage. Produces a payment_mandate §4 artifact that downstream card-specific nodes can consume.

mandate_type: payment_mandate Reused from agentic-policy chain

Open ART-16 →

ART-23 · compliance_control

Visa Trusted Agent Protocol (TAP) Signature Inspector

Parses and scores a Visa TAP Signature-Input / Signature header pair (RFC 9421 HTTP Message Signatures). Also runs a 5-question TAP Readiness Assessment. Produces a compliance_control §4 artifact.

mandate_type: compliance_control T286 promoted RFC 9421

Open ART-23 →

ART-24 · compliance_control

Mastercard Agentic Token Scope Builder

Build or lint a Mastercard Agent Pay Agentic Token scope — agent binding, merchant scope, per-transaction limit, total limit, velocity cap, expiry, MCC allow-list. Validates that the token never exposes the raw PAN to the agent. Produces a compliance_control §4 artifact.

mandate_type: compliance_control T287 promoted MDES · Agent Pay

Open ART-24 →

Branch B — A2A / x402

Follow if ART-22 routes to A2A or x402 stablecoin rails

ART-25 · compliance_control

A2A Agent Card Validator & Extension Checker

Validates an A2A agent-card.json against the v1.0 shape — required identity fields, capabilities, skills, provider, and signed-card JWS block — and confirms AP2/x402 extension declarations. Produces a compliance_control §4 artifact.

mandate_type: compliance_control T283 promoted A2A v1.0

Open ART-25 →

ART-26 · compliance_control

x402 Header Decoder, Payload Linter & 402 Flow Simulator

Decodes base64 PAYMENT-REQUIRED / PAYMENT-SIGNATURE / PAYMENT-RESPONSE headers, lints an exact-scheme PaymentPayload, walks the HTTP-402 flow, and shows the scheme×network matrix. Produces a compliance_control §4 artifact.

mandate_type: compliance_control T277 promoted x402 · exact scheme

Open ART-26 →

ART-03 · settlement_mandate · Reused node

x402 Settlement Cost & Finality Modeler

Rail-selection and finality recommendation across x402 (HTTP 402), Stripe USDC, card, ACH, and SWIFT. Per-transaction cost, eligibility scoring, micropayment support, cross-border flags. Produces a settlement_mandate §4 artifact. Reused from the core OpenChainGraph suite.

mandate_type: settlement_mandate Reused from core suite x402 · Stripe USDC · ACH · SWIFT

Open ART-03 →

Terminal — Both Branches

Run after completing either Branch A or Branch B

⊗

ART-18 · compliance_control · Terminal

MCP Developer Readiness Scorecard

Scores an MCP server implementation across 6 dimensions: tool definitions, auth model (OAuth 2.1), logging, error handling, AP2 integration, and deployment posture. Accepts the execution_hash from any Branch A or Branch B terminal artifact as a parent hash. Produces the final compliance_control §4 OpenChainGraph artifact for the agentic-rail bundle.

mandate_type: compliance_control Reused from agentic-policy chain chain_depth: 2 (after branch)

Open ART-18 →

§4 OpenChainGraph artifact schema — branching chain

{
  "execution_hash": "<SHA-256 over sorted-key {policy_parameters, output_payload}>",
  "chain": {
    "parent_hashes": ["sha256:<upstream node hash>"],  // ART-22 hash in Branch A/B node 1
    "parent_tool_ids": ["art-22-agentic-payments-protocol-comparator"],
    "chain_depth": 1                                    // 0=root, 1=first branch node, 2=terminal
  },
  "policy_parameters": { ... },
  "output_payload": { ... }
}

§4 Execution Hash · Chain Definition Anchor

execution_hash:computing…

Export Artifacts

Download the §4 chain definition artifact (hash-anchored composite JSON) or the §13.11 W3C Verifiable Credentials view. Both derive from the chain definition — no new hash is minted. Available after hash computation.

Agentic Rail Chain