Selling to agents

An Agent buyer finds an Offer by reading, decides by parsing, and pays inside its own Limits. Every Startup is purchasable by Agents from the day it goes Live.

Why Agent buyers matterCopy Anchor Link

A growing share of purchases starts with an Agent. A coding Agent picks the API it calls, and a procurement Agent compares three vendors before a person reads any of them. The Startup that an Agent can find, understand, and pay without help wins the call.

The Plays that reach Agent buyers are the cheapest in the catalog. Agent registries, Agent-to-agent selling, and answer engine optimization rate 5 for scalability and 1 for cost. Few sellers are ready for Agent buyers, so a Startup that is ready holds a position human channels no longer offer.

How an Agent finds a StartupCopy Anchor Link

At Live, every Startup publishes the machine registers an Agent reads: OpenAPI, llms.txt, a Markdown copy of every page, agents.json, and an MCP server. It lists itself on the MCP Registry and the other Agent registries under its own Domain.

An Agent picks a tool by its description, the way a person picks a search result by its title. So SalesBuilder tests tool descriptions against Agent tool search, as an Experiment with a fixed threshold. A tool call is usage, and registry rank follows calls, not listings.

Quote, then chargeCopy Anchor Link

Every priced Verb quotes before it charges. The quote states the Price, the unit, and how long the quote holds, so the Agent knows the cost before it commits.

tariffcodes.dev classifies goods into customs codes at $0.04 a classification. A freight Agent sends 300 product descriptions, reads a quote for $12.00, and checks it against its remaining spend Limit. It proceeds, and the Meter records 300 Entries, exactly once each.

The 402 replyCopy Anchor Link

A call outside the caller's Entitlements gets a 402 reply. The reply is a standard problem document, and its next link accepts the Offer that covers the call.

{
  "type": "https://startupbuilder.dev/code/api/errors/payment-required",
  "title": "Payment required",
  "status": 402,
  "detail": "classify is part of offer per-call at $0.04 per classification.",
  "fix": "Accept the Offer named in next, then retry the call.",
  "next": "https://api.sb/tariffcodes.dev/offers/per-call/accept"
}

The Agent accepts the Offer, pays from its own Mandate, and retries the call with the same idempotency key. It needs no signup, no key issued by a human, and no sales conversation.

Unknown AgentsCopy Anchor Link

An Agent with no history with the Startup is an unknown Agent. It pays before it calls, inside a small first spend Limit the seller sets per Offer. Each paid, undisputed call raises its standing, and its Limit grows with that history.

The buyer side carries its own controls. A buying Agent spends through Agent payments under a Mandate that caps each charge and each period. A charge above its Limit creates an Approval on the buyer's side, never a surprise on the seller's.

Who the Customer isCopy Anchor Link

The Agent that calls is not always the party that owes the money, and the Motion of the Offer records the chain. In b2a, the Agent buys for itself. In b2a2b, b2a2c, and b2a2d, it buys for a business, a consumer, or a developer.

The Customer is the party that pays: the Agent in b2a, the principal in the others. Every Action records whom it was by and whom it was for, so receipts, Limits, and support reach the right party.

Agent buyers are counted as Customers, not as traffic. A paid call from an unknown Agent counts toward outside revenue the same as a card payment from a person.

What an Agent readsCopy Anchor Link

An Agent buyer reads differently from a human one. It needs schemas, acceptance rules, latency, error behavior, and a Price it can parse. The Offer is the same; the page it reads is not.

Docs come first for Agents: Markdown, OpenAPI, and examples that run. A Startup measures time to first successful call, and anything above five minutes is the week's one change.

NextCopy Anchor Link

• Offers and pricing: the Offers an Agent accepts.
• Customers: who pays when an Agent acts.
• b2a: the Motion where an Agent buys for itself.