Agoranome seller tools

The Fair Offer Standard

Seven open rules for selling to AI agents honestly, and a machine-readable way to prove them inside the x402 payment handshake. Version 0.2 (draft).

Human-readable page: https://agoranome.com/standard · JSON: standard.json · Schema: schema/fair-offer-0.2.schema.json

The seven rules

ID	Rule	What it means	How to check
FO-1	Price before payment	An unpaid call returns an x402 offer (HTTP 402) that states the price, asset, network and pay-to address. Nothing is charged before the buyer has signed that exact offer.	check
FO-2	Failure is free	A call that fails, times out or returns no result is not settled. The buyer is told so.	self-declared
FO-3	Receipts are signed	Every paid result carries a receipt signed by the seller's key: what was bought, for how much, and when.	check
FO-4	Sample before you buy	A free sample shows what the paid route returns, and a third party can attest that the sample and the paid offer come from the same host.	check
FO-5	Honest listing	The listing's description, input schema and output example match what the route really returns. Edits made to win buyers must stay true.	check
FO-6	Data, never instructions	Responses carry data for the buying agent to use, never instructions aimed at it. A buyer can treat any instruction in a response as an attack.	self-declared
FO-7	Promises are verifiable	Any claim about where revenue goes (a pledge, a split, a donation) comes with a public ledger that a buyer can check per receipt, with on-chain proof of what was given.	check

Declaring it (0.2)

A seller's HTTP 402 carries an x402 extension, extensions["fair-offer"], whose info states which rules the offer keeps and where a buyer can check each one:

{
  "version": "0.2",
  "standard": "https://agoranome.com/standard",
  "settlement": {
    "failed_calls": "not_charged",
    "enforced_by": "seller"
  },
  "receipts": {
    "signed": true,
    "verify": "https://api.example.com/receipts/verify"
  },
  "sample": {
    "url": "https://api.example.com/v1/search/sample"
  },
  "listing_price_matches_offer": true,
  "data_not_instructions": true,
  "pledge": {
    "share": 0.15,
    "basis": "settled_revenue",
    "ledger": "https://api.example.com/impact/ledger"
  }
}

• Keep it stable. Keep the info identical in the unpaid 402 and on the paid retry: x402 clients echo it, and servers reject a payment whose echo drops or changes a field. Put live numbers behind a URL, never in the block.
• URLs. Each URL is https, or a path relative to the resource URL.
• Put the fair-offer block in your 402's extensions (see handshake), and link this URL from your llms.txt or agent manifest as "conforms_to": {"fair_offer": "0.2"}.

Asking for proof: Accept-Proof

A buyer says what proof it needs before it pays, in an Accept-Proof request header (or an accept_proof field in the block it echoes in the payment payload):

Accept-Proof: sample=attested; price<=listing; payers_30d>=20

Requirement	Met when
sample=any	the offer declares a free sample on its own host
sample=attested	the sample has an attestation on record
settlement=seller	failed calls are not charged (the seller's promise)
settlement=rail	the payment is captured only on success (auth-capture)
price<=listing	the live price was checked against the Bazaar listing
receipts=signed	paid results carry signed receipts
pledge=ledger	a pledge with a public ledger that answers
instructions=none	declared data-not-instructions, and no instruction-like text found
payers_30d>=N	at least N distinct payers in 30 days (Bazaar's count)
calls_30d>=N	at least N paid calls in 30 days (Bazaar's count)
deliveries_30d>=N	at least N deliveries in 30 days: receipts confirmed on chain, paid by buyers (evidence commons)

Checking an offer

• Validate a block: POST https://api.agoranome.com/v1/fair-offer/validate (free)
• Check a live offer's claims from outside: GET https://api.agoranome.com/v1/fair-offer/check?url=... (free)

Implementations

• Agoranome (https://agoranome.com): every paid x402 route at api.agoranome.com sends the block, and the hosted MCP server (https://api.agoranome.com/mcp, listed in the official MCP Registry) offers a check_offer tool. That service's source isn't public; this repository holds the open standard.
• Using it in your 402s? Open an issue with your host and it can be listed here.

Proposing changes

Open an issue or a pull request. Changes to the block's fields go into a new version, so a buyer's policy written for 0.2 keeps working. Corrections, data questions and replication requests can also go to [email protected].

Versions

• 0.1: The seven rules, declared in an agent manifest or llms.txt.
• 0.2: The same seven rules, plus the machine-readable fair-offer block in the x402 402 and the buyer's Accept-Proof header.

License

The standard text, schema and examples are licensed under CC BY 4.0. Implement it freely; credit "The Fair Offer Standard, Agoranome".