Paying for x402 Services

Use the npx agnic@latest x402 pay command to call x402-enabled API endpoints with automatic USDC payment on Base.

Confirm wallet is initialized and authed

npx agnic@latest status

If the wallet is not authenticated, refer to the authenticate-wallet skill.

Command Syntax

npx agnic@latest x402 pay <url> [-X <method>] [-d <json>] [-q <params>] [-h <json>] [--max-amount <n>] [--json]

Arguments & Options

Option	Description
<url>	Full URL of the x402-enabled API endpoint
-X, --method <method>	HTTP method (default: GET)
-d, --data <json>	Request body as JSON string
-q, --query <params>	Query parameters as JSON string
-h, --headers <json>	Custom HTTP headers as JSON string
--max-amount <amount>	Max payment in USDC atomic units (1000000 = $1.00)
--correlation-id <id>	Group related operations
--json	Output as JSON

USDC Amounts

X402 uses USDC atomic units (6 decimals):

Atomic Units	USD
1000000	$1.00
100000	$0.10
50000	$0.05
10000	$0.01

Input Validation

Before constructing the command, validate:

• url: Must be a valid HTTPS URL (^https://[^\s;|&]+$). Reject URLs containing spaces, semicolons, pipes, or backticks.
• method: Must be one of GET, POST, PUT, DELETE, PATCH (case-insensitive).
• data: Must be valid JSON. Parse it first; reject if parsing fails.
• max-amount: Must be a positive integer (^\d+$).

Do not pass unvalidated user input into the command.

Workflow

1. Check requirements first (optional but recommended):

   npx agnic@latest x402 details <url>
   

   This shows the price, method, and schema without making a payment.

2. Verify balance:

   npx agnic@latest balance --network base
   

3. Make the paid request:

   npx agnic@latest x402 pay <url> --json
   

Examples

# Make a GET request (auto-pays)
npx agnic@latest x402 pay https://example.com/api/weather

# Make a POST request with body
npx agnic@latest x402 pay https://example.com/api/sentiment -X POST -d '{"text": "I love this product"}'

# Limit max payment to $0.10
npx agnic@latest x402 pay https://example.com/api/data --max-amount 100000

# Get JSON output
npx agnic@latest x402 pay https://example.com/api/weather --json

Prerequisites

• Must be authenticated (npx agnic@latest auth login)
• Wallet must have sufficient USDC balance on Base

Error Handling

Common errors:

• "Not authenticated" — Run npx agnic@latest auth login first
• "Insufficient balance" — Fund wallet with USDC (npx agnic@latest balance to check)
• "No X402 payment requirements found" — URL may not be an x402 endpoint
• Invalid JSON in --data — Ensure the body is valid JSON before passing
• HTTP 4xx/5xx from the API — Show the status code and response body to the user