What are L402 agent payments?

L402 agent payments let an API return an HTTP 402 payment challenge that an autonomous agent can satisfy with a Lightning payment before receiving access.

Why use L402 for robot customers?

Robot customers need programmatic, low-friction payment. L402 combines HTTP 402, Lightning invoices, and access credentials so agents can pay for APIs without manual checkout.

Is SatGate Charge the same as Fiat402?

No. SatGate Charge is L402 Lightning for request-path agent/API payments. Fiat402 is a separate concept and should not be conflated with Charge.

L402 Lightning payments for autonomous agents

Let AI Agents Pay for APIs Like Customers

SatGate Charge uses L402 Lightning payments to let robot customers unlock protected APIs, tools, datasets, and premium capabilities at request time.

Read the L402 guide Monetize APIs

The next API customer is not always a human

AI agents increasingly discover, evaluate, call, and combine APIs on behalf of people and companies. That creates a new customer type: software that can decide an API is worth paying for right now.

Traditional API monetization assumes a human signs up, enters a card, picks a plan, stores a key, and then integrates. Robot customers need a request-native flow: ask for resource, receive price, pay, unlock access, continue task.

L402 gives that flow an internet-native shape. SatGate puts it in front of APIs as the Charge mode of the economic control plane.

Good fits for L402 agent payments

Premium search, research, or enrichment endpoints.
Datasets agents query occasionally but value highly.
AI tools sold per use instead of by seat.
MCP tools exposed to external agent ecosystems.
APIs where authorization and payment should happen together.

How L402 agent payments work with SatGate

SatGate sits in the request path. The API stays protected while the agent receives a machine-readable price and payment challenge.

Agent requests a resource

An autonomous agent calls a protected API, model, dataset, tool, or premium endpoint.

SatGate returns a 402 challenge

Instead of a subscription flow or sales gate, SatGate issues an L402 payment challenge tied to the request.

Agent pays with Lightning

The robot customer pays the invoice through a wallet such as SaturnZap or another L402-capable client.

Proof unlocks access

SatGate verifies payment and releases a scoped credential or forwards the approved request.

Usage is attributed

Every paid request is tied to agent identity, route, price, policy, and settlement evidence.

API revenue becomes native

APIs can charge autonomous agents per request, per tool, per dataset, or per premium capability.

A robot-customer request flow

# Agent attempts a protected API call
sz fetch https://api.example.com/premium-research --max-sats 25

# SatGate replies with an L402 challenge
HTTP/1.1 402 Payment Required
WWW-Authenticate: L402 invoice=lnbc..., macaroon=...

# Agent pays, presents proof, and receives the resource
HTTP/1.1 200 OK
{ "answer": "paid premium result" }

In this pattern, the merchant runs SatGate. The robot customer runs a wallet/client. Payment, authorization, and audit happen before upstream access.

OBSERVE

See agent demand

Understand which agents and routes create monetizable demand before forcing a pricing model.

CONTROL

Protect access

Limit which agents, routes, prices, budgets, and proofs are accepted before unlocking protected resources.

CHARGE

Collect per request

Use L402 Lightning payments to charge autonomous agents for API access at the moment of demand.

Turn protected APIs into robot-customer products

SatGate gives API teams a request-path control plane for observing, controlling, and charging AI agents. Charge is L402 Lightning: simple, programmatic, and built for autonomous access.

Try the payment demo HTTP 402 use cases