Trust registry

The wallet's answer to "who may be paid at all". An open format of signed receiver descriptors + a federation of commercial verification providers. The first provider is 4agents (verified merchants and, by extension, verified paid MCP servers).

Why a separate layer

A mandate that lists receivers directly works for a couple of tools but does not scale: a principal cannot manually vet every new MCP server or shop. The registry moves the vetting ("the receiver is real: owns the domain, paid for verification, has history") to a provider the principal trusts once — with one line in the mandate:

"allow": [ "registry:4agents/verified" ]

Semantics: "anyone whose descriptor is signed by provider 4agents at level verified or above may be paid."

Receiver descriptor

One format for both the registry and self-hosted /.well-known/stipendex.json:

{
  "stipendex": "receiver/0.1",
  "id": "mcp:exa-search",
  "name": "Exa Search",
  "keys": [ "ed25519:GfHq…" ],
  "endpoints": { "mcp": "https://mcp.exa.ai", "http": "https://api.exa.ai" },
  "rails": [ { "scheme": "account", "facilitator": "https://pay.4agents.io" } ],
  "profiles": [ "service" ],
  "trust": {
    "provider": "4agents",
    "level": "verified",
    "verified_at": "2026-06-01T00:00:00Z",
    "expires_at": "2026-09-01T00:00:00Z",
    "evidence": [ "domain", "payment", "feed" ]
  },
  "sig": "<registry provider JWS>"
}

Key rules:

• T1. The key in quote.receiver.key MUST match one of the descriptor's keys[] — receiver substitution under a trusted name is impossible.
• T2. A descriptor expires (trust.expires_at, SHOULD ≤ 90 days) and is re-issued; revocation = non-reissue + the provider's revocation list, which the wallet checks on the first payment to a receiver and then per cache TTL.
• T3. trust.level is the provider's scale; the provider must publish what each level means (what was checked). For 4agents: verified = domain ownership + a working payment + a valid feed; trusted+ = KYC + transaction history.

Provider API (minimum)

GET /registry/receivers/{id}     → descriptor (JWS)
GET /registry/revocations        → revoked ids/keys (JWS, incremental)
GET /registry/meta               → provider keys, level definitions

Wallets cache descriptors per TTL; offline validation — by the provider's signature.

Federation

There can be many registries (per industry, jurisdiction, ecosystem). The principal lists trusted providers in the mandate; the wallet accepts a descriptor from any of them. Providers compete on verification quality — like certificate authorities, but with a transparent scale and no single global root.

Provider economics

Verification is paid by the receiver (the 4agents model: a subscription for verified). That is both a spam barrier and the provider's business. For wallets and principals the registry is free — they are the customers of trust, not a revenue source.

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