Guides
What is x402? Pay-per-call APIs for AI agents, explained
x402 lets a service charge for an HTTP request with no signup or API key: the server answers 402 Payment Required, the client pays in stablecoin, and retries. Here is how it works and why it fits autonomous agents.
Double-entry accounting for AI agents
An autonomous agent that earns and spends money needs more than a running total. Double-entry accounting gives it self-checking, auditable books. Here is the model in agent terms, with the five account types and the sum-to-zero invariant.
Quickstart: give your AI agent a ledger in five calls
A copy-paste walkthrough: create two accounts, post a balanced transaction, and pull a trial balance against the live Ledger API — paying per request with x402, or with a capability token.
How to track an AI agent's spending and revenue
A worked example: model an agent that earns fees and pays for tools as double-entry accounts, record each event as a transaction, and read its profit with a trial balance — all over HTTP.
Capability tokens vs x402: which auth model for your agent?
Ledger supports two auth models — pay-as-you-go x402 micropayments and standing Ed25519 capability tokens with Reader/Writer/Owner scopes. Here's an honest comparison and when to use each.
A ledger API vs building your own bookkeeping: buy vs build
Should you rent a double-entry ledger API or build accounting into your agent yourself? An honest look at what you'd have to build, when DIY makes sense, and when renting wins.