Explainers
Understand the rails before you sell on them.
New · 12 Sep
What is Universal Commerce Protocol (UCP)?
How Google and Shopify's open commerce standard lets agents discover merchant capabilities, negotiate checkout and payment handlers, and carry commerce state across MCP, A2A and other transports.
New · 12 Sep
What is Pine Labs P3P?
How P3P uses HTTP 402, delegated mandates and verifiable receipts for agent payments—and why sharing a 402 status code does not make P3P the same as x402.
New · 12 Sep
What is India's Unified Agentic Protocol?
What is reported, what NPCI has actually published, and how an AI-agent registry, UPI Circle, Reserve Pay and bounded authority could fit together.
New · 12 Sep
What is Agentic Commerce Protocol (ACP)?
How OpenAI and Stripe's open commerce spec connects product discovery, merchant state, checkout, delegated payments and MCP—and how ACP differs from x402.
New · 12 Sep
What is Mastercard Agent Connect?
How AI agents discover merchant catalogs, build carts and reach payment—and how Agent Connect differs from Agent Pay, MCP and x402.
New · 11 Sep
What is Ant's Agentic Mobile Protocol?
AMP's wallet-first agent-payment model, delegated authority, KYA, nano A2A settlement and the September rollout across wallets and acquirers.
Updated 11 Sep
What is WebMCP?
How websites expose structured tools to browser agents, how WebMCP differs from MCP, and what ChatGPT Site Tools support today.
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 the machine economy?
Software that discovers, pays, works and settles with other software — with humans setting budgets and rules.
What is an agent wallet?
A spending envelope a machine can use, with policy, not a seed phrase pasted into a prompt.
How does a 402 payment work?
Call, challenge, pay, retry, verify.
What is agent engine optimization?
Make a machine able to discover, understand, trust, select, pay and reuse a service. Do not keyword-stuff HTML as a substitute.
x402 vs MPP
Two HTTP 402 families. Different payloads, facilitators, and settlement stories.
How do AI agents pay each other safely?
Use x402, MPP or another machine-payment rail only after code-enforced checks for amount, asset, network, payee, resource and remaining budget.
What is an AI agent?
Software that can take a goal, use tools, and act — not a chat window with a personality.
What is a machine-payment rail?
The rules, asset, network and verifier that let software settle without a checkout page.
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 for AI agents?
A bounded machine purchasing loop: discover suppliers, inspect live terms, enforce authority and budget, buy, verify fulfilment, reconcile and reuse.
What is an agent marketplace?
A catalogue where the SKU is a documented outcome other software can buy — not a human app store with extra AI copy.
Machine catalog
Public titles from the learn API.
Bodies that are not on this site stay on https://api.zfinia.com/v1/learn. Title and dek only — lesson bodies that are not on this site stay on the machine API.
Software that can take a goal, use tools, and act — not a chat window with a personality.
Software that discovers, pays, works and settles with other software — with humans setting budgets and rules.
An open protocol that uses HTTP 402 so a client can pay a server, usually in USDC, and retry.
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.
A deterministic or bounded result with a schema, a price, and usage rights.
[redacted]
Call, challenge, pay, retry, verify.
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.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Delegate spend, never delegate the root key.
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.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
Cross-protocol payment compatibility
Practical machine-economy lesson. Not a guaranteed-income pitch.
Practical machine-economy lesson. Not a guaranteed-income pitch.
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.
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.
tools/list describes input schema. tools/call does one job. Payment is an overlay.
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.
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.
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.