Introspect the MCP's payment capabilities: which wallets are configured, spending limits, and stored credential count. Call this first to understand what payment methods are available.

Probe an endpoint to discover its L402 pricing without committing to payment. Returns the cost in sats, available payment methods, and credit tiers (if toll-booth server). The challenge is cached so a subsequent l402-pay can reuse it.

Fetch a URL with automatic payment handling (L402 Lightning + x402 on-chain + ecash and LUD-25 bearer notes). Manages credentials, pays automatically when autoPay is true and cost is within budget, and retries. For human wallets, returns a payment page URL or QR code. For x402 services, returns payment details (receiver address, network, asset, amount) — the user pays in their wallet and provides the transaction hash. Set autoPay to true for seamless access. When a 402 is returned with tiers, present the pricing options to the user and use l402-buy-credits to purchase their chosen tier. For widget hosts, call l402-fetch-preview first to show a payment confirmation dialog before spending.

Confirm payment and store credentials. Call this after l402-fetch returns a 402 with a paymentHash — polls the payment server for settlement (up to 30s for human wallet), then stores the credential so the next l402-fetch succeeds. For human wallets, call this immediately after showing the payment URL to the user.

List all stored L402 credentials. Shows origin, cached credit balance, and server type. Balance values are cached and may be stale; check lastUsed timestamp.

Check cached credit balance for a server. Returns the last known balance from the credential store without making a network request. The "stale" flag is true if the balance was last updated more than 5 minutes ago.

Store an L402 token (macaroon:preimage) obtained from a payment page. Use this when a user pastes back a token from a toll-booth payment page. The token is stored as a credential so subsequent l402-fetch calls are authenticated.

Buy credits from a toll-booth server with volume discounts. Omit amountSats to discover available tiers. Provide amountSats to purchase a specific tier. Only works with toll-booth servers.

Redeem Cashu ecash tokens directly on a toll-booth server, avoiding the Lightning round-trip. Handles the two-step flow automatically (create invoice then redeem token). Only works with toll-booth servers.

Search for paid APIs and services. Use this when the user wants something that might be available as a paid service — jokes, data, AI, content, etc. Discovers services announced on Nostr and returns their URLs, pricing, and capabilities. Then use l402-fetch with the URL to access the service.

Preview payment requirements for a URL without spending any sats. Returns cost, protocol, and payment method so a confirmation dialog can be shown. Use this before l402-fetch to give the user a chance to approve or cancel payment. For widget hosts, the result drives a payment confirmation dialog.