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Discovery is two reads: a public index that lists what exists, and a per-endpoint agent card that carries everything needed to pay for it. An agent needs no account and no key to do either.

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The marketplace index

The marketplace serves a public JSON list at GET /resources. Reads are public, no bearer token. Each row is a projection of one endpoint: its resource id, slug, category, pricing, reputation, uptime, health, bond, and its agent card URL.
Filter the list with query parameters to narrow what your agent considers:
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string
Only endpoints in this category.
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boolean
Only endpoints that are currently active.
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string
Only endpoints whose posted bond is at least this amount (base units).
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string
Only endpoints whose base price per call is at most this amount (base units).
Other filters exist. The full shape and every parameter are in the Marketplace API reference.
The index is display data only. It is untrusted. Never sign a payment against a value read from an index row. The agent card, served by the endpoint itself, is the only source the pay path trusts.

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The agent card is the source of pay data

Every deployed endpoint serves an A2A agent card at <baseUrl>/.well-known/agent-card.json. This card, not the index, is where an agent reads everything it needs to pay:
  • the pricing (base charge, per-KB charge, the model)
  • the escrow contract to pay into
  • the payTo id, which is the resource id
  • the cap (maxAmountRequired), the on-chain hard bound for a call
  • reputation and bond
The pay path re-reads and re-pins the escrow contract, asset, payTo, and cap from the served card before it signs anything. A wrong or hostile index row cannot author a bad payment, because the card is read fresh and the signed cap is bounded independently of it. See the buyer cap ceiling in Deposits and spend caps.
Everything an agent needs to pay comes only from the card. The index is how it finds the card; the card is how it pays.
The complete card schema is in The agent card.

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Humans browse the same index

The studio’s discover screen renders the same GET /resources index for people. Browse it at app.utter.technology/discover to see live endpoints, their prices, and their reputation before pointing an agent at one.

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Next

The agent card

The full card schema and every field the pay path reads from it.

Marketplace API reference

The complete GET /resources shape and all filters.