Understand the rails before you sell on them.

Machine catalog

Public titles from the learn API.

Bodies that are not on this site stay on https://api.zfinia.com/v1/learn. This index is title and dek only — not private Foundry IP.

• What is an AI agent?

  Software that can take a goal, use tools, and act — not a chat window with a personality.

• What is the machine economy?

  Software that discovers, pays, works and settles with other software — with humans setting budgets and rules.

• What is x402?

  An open protocol that uses HTTP 402 so a client can pay a server, usually in USDC, and retry.

• What is MCP?

  A standard way for models to list and call tools. It is not itself a payment protocol.

• What is a machine-payment rail?

  The rules, asset, network and verifier that let software settle without a checkout page.

• Why would one agent pay another?

  Because fetching, verifying, or computing something is cheaper than guessing.

• What can an agent sell?

  A deterministic or bounded result with a schema, a price, and usage rights.

• What is an agent wallet?

  [redacted]

• How does a 402 payment work?

  Call, challenge, pay, retry, verify.

• What is a paid API?

  An HTTP interface whose unpaid call is a challenge and whose paid call is the documented result.

• What is autonomous procurement?

  Software that buys inputs under a budget, a rights gate and an audit log — not an unconstrained agent with a credit card.

• Build your first agent

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Give an agent external tools

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Create an MCP server

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Expose an API

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Add machine-readable schemas

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Add x402 payment requirements

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Create a paid endpoint

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Give an agent a wallet safely

  Delegate spend, never delegate the root key.

• Discover other paid services

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Build buy → transform → sell workflows

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Measure cost and contribution margin

  Use the calculators. They refuse to forecast.

• Make a service machine discoverable

  Same checklist as the Start-here guide, without a marketplace ranking purchase.

• Agent-to-agent commerce

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Autonomous procurement

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Routing across providers

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Payment orchestration

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Reputation

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Identity

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Settlement

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Accounting

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Evidence and provenance

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Fail-closed treasury controls

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Cross-protocol payment compatibility

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Marketplaces

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Agent discovery

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Machine-native business architecture

  Practical machine-economy lesson. Not a guaranteed-income pitch.

• Build your first paid agent service

  One route, one schema, one exact price, one 402, one deterministic result.

• Build your first x402 API

  A competent developer should leave this page with a working unpaid 402 and a deterministic paid handler.

• Turn an existing API into an agent-purchasable service

  Keep the function. Freeze the JSON contract. Challenge before side effects.

• Build your first MCP tool

  tools/list describes input schema. tools/call does one job. Payment is an overlay.

• Make an agent buy an API

  The buyer needs a wallet under a budget, a 402 client, and the schema.

• Give an agent a safe spending budget

  Use remainingAtomic, maxPerPurchaseAtomic, allowlisted asset/network, kill switch, idempotency.

• Build a buy → add value → sell workflow

  Pay upstream only when rights allow. Sell the derivative, not the raw passthrough.

• How to make an API discoverable to agents

  Outcome, schema, price, rail, live 402. Conformance outranks keyword stuffing.

• How to make money with AI agents (without fairy tales)

  Observe demand, sell a derived outcome, measure repeat payers. No guaranteed income.

• x402 vs MPP

  Two HTTP 402 families. Different payloads, facilitators, and settlement stories.

• Monetize an existing API for agents

  Keep the function. Add a schema, a 402, a price cap, and discovery that matches live behaviour.

• How do agents pay each other?

  Discover a contract, receive a 402 or checkout session, settle under a budget, retry, verify.

• How to identify machine demand before building

  Observe payers and repeat use. Listing count is not demand. Comments are signals.

• How to calculate marginal cost and contribution

  Price minus variable cost minus failure. Arithmetic, not a forecast.

• How agent wallets should be controlled safely

  Policy plus arithmetic. The model proposes. Limits decide. Missing config is a stop.