Documentation

AgentFuse docs

AgentFuse lets an AI agent pay for APIs and compute on without holding your funds. You fund a vault, sign rules, and give the agent a key that can only request payments. Each request is checked against the rules before anything is signed and ends up as a receipt.

Quickstart

Open the dashboard and connect the wallet that will own the vault.
Create a fuse: name the agent, set the daily budget, per-call cap, call limit, expiry and allowlist, and make the first deposit in USD.
Copy the agent key and put it in your agent environment as AGENTFUSE_KEY.
Wrap paid calls with the SDK. Watch them land in Activity.

Agent SDK

npm i @agentfuse/sdk
pip install agentfuse

fuse.fetch() behaves like fetch. When the endpoint answers 402 Payment Required, the SDK sends the quote to the vault with a fresh intent ID, waits for the decision and retries the request with the payment proof.

import { Fuse, FuseDeclined } from "@agentfuse/sdk";

const fuse = new Fuse({ key: process.env.AGENTFUSE_KEY });

try {
  const res = await fuse.fetch("https://api.lumensearch.io/v1/query", {
    method: "POST",
    body: JSON.stringify({ q: "x402 facilitators on solana" }),
    intent: "task-1842/search-3", // optional: your own idempotency key
  });
  console.log(res.receipt.amount, res.receipt.signature);
} catch (e) {
  if (e instanceof FuseDeclined) console.log(e.reason); // "budget_exceeded"
}

Retrying with the same intent never pays twice: the vault returns the existing receipt. The same intent with a different payee or amount is refused.

Rules

Rule	What it limits
Daily budget	Total USD the agent may spend per UTC day. Spent and reserved both count.
Per-call cap	Highest single quote the vault will pay.
Paid calls per day	Stops loops that make many small payments.
Allowlist	Exact HTTPS hosts and paths, matched after normalization. Redirects do not widen it.
Expiry	After this date the agent can pay nothing until you sign new rules.
Pause	Immediate stop for new payments. Signed payments still settle.

Rules are versioned. Each update is signed by the owner wallet with a higher version number; older versions cannot be replayed. Updating rules never resets today's spent or reserved amounts.

Budget model

available = daily_budget − spent − reserved

An approved request reserves its amount before signing. Parallel requests are serialized per vault, so they can never overshoot together.
Once settled, the reservation turns into spent. A reservation is released only when the payment provably cannot settle.
Lowering the budget below today's spend just blocks new payments; available shows zero.
The day rolls over at 00:00 UTC. History and receipts are kept.

Decline reasons

Code	Shown as	Meaning
`not_allowlisted`	Recipient not on the allowlist	Payee host or path is not on the allowlist, or the quote points to a different recipient.
`over_call_cap`	Price above the per-call cap	The quoted price is above the per-call cap.
`budget_exceeded`	Would exceed today's budget	Spent + reserved + this quote would go over today's budget.
`call_limit`	Daily call limit reached	Today's paid-call limit is used up.
`vault_empty`	Vault balance too low	The vault holds less than the quote.
`expired`	Rules expired	The rules passed their expiry date.
`paused`	Fuse is paused	The owner paused the fuse.
`revoked`	Agent key revoked	The agent key was revoked.
`duplicate_intent`	Intent already paid	This intent ID was already paid; the original receipt is returned instead.

Receipts

Every request produces a receipt, paid or not: intent, rules version, quote, payee, amount, protocol fee, signature, timestamps and status. Payment status (reserved → settled) and API result (delivered / provider_error / timeout) are tracked separately, so a paid error is still visible as a spend. Export as CSV, or share a single receipt as a public link without agent details.

Security model

The vault is a program account owned by your wallet. The agent key can request payments; it cannot withdraw, change rules or sign arbitrary transactions.
Only plain USD transfers to allowlisted payees are built. Unknown instructions, extra transfers or account creation in a quote are declined.
Keys and wallets you give an agent outside AgentFuse are outside this protection.

Fees

0.5% of each settled payment. Declined requests are free. All protocol fees buy back and burn $TOKEN — see the burn ledger. Network fees are paid by the vault in SOL and shown separately.