5arz — Proof-of-Human MCP server

Prove a real, unique human performed an action — and mint a signed credential anyone can verify, offline, without trusting us.

Live endpoint: https://mcp.5arz.com (Streamable HTTP) Docs: https://5arz.com/mcp · Free sandbox key: no card, no sales call

Why this exists

AI agents now solve CAPTCHAs faster than people do, and the fastest-growing "user" on the web is an agent acting for a real customer. That breaks the question everything was built around.

CAPTCHA asks "can this session pass a puzzle?" — a negative filter that treats a helpful agent and an abusive bot identically.

5arz answers a different question: "is there a real, unique human behind this action, and can they prove it to everyone downstream?" That is a credential problem, not a puzzle problem.

Web Bot Auth, Know Your Agent and the Trusted Agent Protocol all reference a verified human principal. None of them provide one. This is that layer.

Related MCP server: soulprint

What you get

A signed ES256 JWT, verifiable against a public JWKS with any JWT library:

{
  "iss": "https://5arz.com",
  "vct": "https://5arz.com/credentials/proof-of-personhood",
  "sub_hash": "…",
  "unique_human": true,
  "liveness": true,
  "assurance": "direct_document_liveness",
  "verified_by": "https://5arz.com",
  "method": "didit_document+passive_liveness+face_match",
  "exp": 1790000000
}

Two properties worth understanding:

You never have to trust us. Verification runs against https://api.5arz.com/.well-known/jwks.json. No SDK, no callback, no dependency on our uptime — or our continued existence. A receipt only the issuer can validate is worth what an assertion is worth.

The credential states its own provenance. assurance, verified_by and method say how the human was established. A credential from a partner's own KYC is labelled partner_asserted and does not claim liveness we did not run. unique_human is only ever true when uniqueness was actually checked. A credential is worth exactly the weakest thing that can produce it, so we make the difference machine-readable instead of hiding it.

Tools

Quick start

# free sandbox key — unlimited, credentials marked test:true
curl -X POST https://api.5arz.com/api/agents/register \
  -H 'content-type: application/json' \
  -d '{"name":"My Agent","contactEmail":"you@co.com","mode":"test"}'

Add to an MCP client:

{ "mcpServers": { "5arz": { "url": "https://mcp.5arz.com" } } }

Verify a credential yourself

Nothing below calls 5arz:

import jwt, requests
jwks = requests.get("https://api.5arz.com/.well-known/jwks.json").json()
key  = jwt.PyJWKClient("https://api.5arz.com/.well-known/jwks.json") \
          .get_signing_key_from_jwt(token)
claims = jwt.decode(token, key.key, algorithms=["ES256"],
                    options={"verify_aud": False})
assert claims["iss"] == "https://5arz.com"
assert claims["unique_human"] is True

Connecting your own users

If you run a product and want your users verified, you do not need them to have a 5arz account:

• You have no IDV — POST /api/agents/verify-link returns a hosted link. Send your user; a signed credential arrives at your webhook.

• You already verify your own users — POST /api/agents/humans/assert. We mint, label it partner_asserted with your method, and do the rest: signing, uniqueness, revocation, delegation, reporting.

Or drop the button on any page:

<script src="https://api.5arz.com/verify.js"
        data-site="agt_your_id" data-ref="your-user-id" async></script>

Verified once, reusable anywhere. Returning humans re-prove with a passkey — no document, no vendor call.

The browser result is advisory. The authoritative path is the credential.issued webhook to your server. Never gate access on a postMessage — your own users can forge it in devtools.

Run it yourself

npm install
npm test            # protocol conformance
npx wrangler deploy

Status

101 verified humans · 18 countries · 5,740 verified completions. Patents pending US 63/979,052 · US 63/979,474.

The verification format is deliberately open. A credential nobody can independently check has no value.

License

Apache-2.0 — see LICENSE.