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<title>SAM Protocol — The Signed Envelope for Agent-Ready Merchants</title>
<meta name="description" content="SAM is the signed envelope that composes UCP, AP2, MCP, ACP, and A2A into one verifiable, time-bounded entry point. Merchant-signed. Locally enforced. Open standard." />
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<meta property="og:description" content="Publish one signed file. Reference everything else. SAM composes UCP, AP2, MCP, ACP, and A2A into a verifiable, time-bounded entry point for AI agents." />
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    <a href="/" class="brand">SAM Protocol</a>
    <nav>
      <a href="#what">What</a>
      <a href="#composes">Composes</a>
      <a href="#how">How</a>
      <a href="https://github.com/SAM-protocol/SAM-Protocol">GitHub</a>
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<main class="wrap">

  <span class="tag">draft-sam-protocol-v2.2</span>
  <h1>The signed envelope for agent-ready merchants.</h1>
  <p class="lede">Publish one signed file. Reference everything else. SAM composes UCP, AP2, MCP, ACP, and A2A into a single, verifiable, time-bounded entry point for AI agents.</p>

  <p>
    <a class="cta" href="https://github.com/SAM-protocol/SAM-Protocol">View on GitHub</a>
    <a class="cta secondary" href="/.well-known/sam.json">See a sam.json</a>
  </p>

  <h2 id="what">What SAM is — and is not</h2>
  <p>SAM is <strong>not</strong> another commerce protocol. The agentic commerce stack of 2026 already has plenty: UCP for capabilities, AP2 for user authorization, MCP for tools, ACP for catalogs, A2A for agent-to-agent. What it lacks is a single, signed, time-bounded entry point that tells an agent which of those a given merchant publishes — and within which bounds autonomous action is permitted.</p>
  <p>SAM is that entry point. A merchant publishes one signed <code>sam.json</code> at <code>/.well-known/</code>. Agents read it, verify an <code>ed25519</code> signature over the entire envelope including its references (RFC 9421), and act only within the merchant-issued policy mandate declared inside.</p>

  <div class="pull">SAM does not replace UCP, AP2, MCP, ACP, or A2A. SAM is the signed envelope that makes any combination of them verifiable in one place.</div>

  <h2 id="composes">How SAM composes with the rest</h2>
  <table>
    <thead>
      <tr><th>Layer</th><th>Standard</th><th>Question it resolves</th></tr>
    </thead>
    <tbody>
      <tr><td>Signed entry</td><td><strong>SAM</strong></td><td>Who is this merchant, what do they publish, is it current, is it genuine, within which bounds may I act?</td></tr>
      <tr><td>Capabilities</td><td>UCP</td><td>What can be browsed, quoted, ordered?</td></tr>
      <tr><td>User authorization</td><td>AP2 (FIDO)</td><td>Did the user authorize this purchase?</td></tr>
      <tr><td>Tool invocation</td><td>MCP</td><td>How does the agent call a specific function?</td></tr>
      <tr><td>Catalog feed</td><td>ACP</td><td>What is in stock, at what price?</td></tr>
      <tr><td>Agent-to-agent</td><td>A2A</td><td>How do two agents collaborate?</td></tr>
    </tbody>
  </table>
  <p>A merchant already on UCP adopts SAM in ten lines: a <code>sam:composes.ucp</code> entry, a signature, a freshness window. No rewrite. No duplication. No fork. The merchant's existing agent surface becomes verifiable from one place.</p>

  <h2 id="how">How it works</h2>
  <ul>
    <li><strong>Discover</strong> — agent fetches <code>/.well-known/sam.json</code>.</li>
    <li><strong>Verify</strong> — <code>ed25519</code> signature over the entire envelope, including every <code>sam:composes</code> reference (RFC 9421).</li>
    <li><strong>Compose</strong> — agent follows the references to UCP, AP2, MCP, ACP, A2A as published.</li>
    <li><strong>Bound</strong> — the merchant policy mandate declares what an agent may and may not do autonomously. Evaluated locally. No network call.</li>
    <li><strong>Fallback</strong> — when bounds are exceeded or a referenced standard is unreachable, control returns to a human via <code>sam:human</code>.</li>
  </ul>

  <h2>Minimal example — composing envelope</h2>
<pre><code>{
  "sam:version": "2.2",
  "sam:identity": { "domain": "example.com", "legalName": "Example Inc." },
  "sam:signature": { "alg": "ed25519",
                     "validUntil": "2026-08-13T00:00:00Z",
                     "value": "base64(...)" },
  "sam:composes": {
    "ucp": { "href": "/.well-known/ucp", "version": "1.0" },
    "ap2": { "supported": true, "endpoint": "/ap2/checkout",
             "mandateTypes": ["cart","payment","intent"] },
    "mcp": { "href": "/.well-known/mcp", "version": "2025-11-25" }
  },
  "sam:mandate": {
    "grammarVersion": "0.1",
    "autoExecute": true,
    "maxAmount": { "value": 200, "currency": "EUR",
                   "inclusiveOfTaxes": true,
                   "inclusiveOfShipping": true },
    "validityWindow": { "notBefore": "2026-05-13T00:00:00Z",
                        "notAfter":  "2026-08-13T00:00:00Z" },
    "agentClass": "any"
  },
  "sam:agentAuth": { "profile": "rfc9421", "algorithm": "ed25519" },
  "sam:human": { "channels": [
    { "type": "email", "value": "agents@example.com" }
  ]}
}</code></pre>

  <h2>Conformance levels</h2>
  <table>
    <thead>
      <tr><th>Level</th><th>Content</th><th>Claim</th></tr>
    </thead>
    <tbody>
      <tr><td>L0</td><td><code>version</code> + <code>capabilities</code> or <code>composes</code> + <code>human</code></td><td>merchant-ready</td></tr>
      <tr><td>L1</td><td>L0 + <code>identity</code> + <code>signature</code></td><td>agent-ready</td></tr>
      <tr><td>L2</td><td>L1 + <code>mandate</code> + <code>agentAuth</code></td><td>bounded autonomy</td></tr>
    </tbody>
  </table>
  <p>Each level is useful on its own. Conformant agents must not perform autonomous economic action against a merchant below L2.</p>

  <h2>Status</h2>
  <p>Draft specification v2.2 (May 2026). Submitted for consideration at the <a href="https://www.w3.org/community/agent-identity/" style="color:var(--accent)">W3C Agent Identity Registry Protocol Community Group</a>. Contributions welcome on GitHub.</p>

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    <span>© 2026 SAM Protocol Working Group</span>
    <span><a href="https://github.com/SAM-protocol/SAM-Protocol" style="color:var(--muted)">GitHub</a> · <a href="/llms.txt" style="color:var(--muted)">llms.txt</a></span>
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