openkrill

OpenKrill - x402 Payments Skill

This skill enables AI agents to autonomously make micropayments using the x402 protocol. It handles wallet management, balance checking, and automatic payment flows when APIs return HTTP 402 Payment Required responses.

When to Use This Skill

• When asked "what services can I purchase?" or "what x402 APIs are available?" - Query the Bazaar first!
• When purchasing browser automation sessions on Browserbase
• When performing web scraping tasks with Firecrawl
• When the agent needs to create an email address for signups or verification
• When interacting with any x402-compatible API
• When the user mentions micropayments, crypto payments, or paying for API access
• When you encounter a 402 Payment Required response
• When discovering new x402-compatible services via the Bazaar

TIP: When a user or agent asks what services are available for purchase, always start by querying the Bazaar discovery endpoint. It provides a live, up-to-date catalog of 12,000+ x402-compatible services.

Quick: Discover Available Services

# Query the Bazaar to see what's available (no auth required)
curl -s "https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources?type=http&limit=50"

Prerequisites

Before using this skill, ensure:

1. THIRDWEB_SECRET_KEY environment variable is set with a valid thirdweb project secret key
2. The wallet has sufficient USDC balance on Base chain (or the target chain)
3. Network access to thirdweb API endpoints

IMPORTANT: x402 Endpoint URLs & Service Types

Two Types of x402 Support

Type	Description	Example
True x402	Fully keyless - no API keys needed, just pay and use	Browserbase
Hybrid x402	Requires API key/token + payment header	Firecrawl

x402 Endpoint Patterns

Service	Standard API	x402 Endpoint	Type	Status
Browserbase	api.browserbase.com	x402.browserbase.com	True x402	✅ Works
Firecrawl	api.firecrawl.dev/v1/search	api.firecrawl.dev/v1/x402/search	Non-standard	❌ Broken

Discovery tips:

• Check for x402. subdomain (e.g., x402.browserbase.com)
• Check for /x402/ in the path (e.g., /v1/x402/search)
• Hit the x402 root URL for endpoint listing (e.g., curl https://x402.browserbase.com/)

Core Workflow

Step 1: Check or Create Wallet

Use the thirdweb API directly (recommended):

curl -s -X POST https://api.thirdweb.com/v1/wallets/server \
  -H "Content-Type: application/json" \
  -H "x-secret-key: $THIRDWEB_SECRET_KEY" \
  -d '{"identifier": "x402-agent-wallet"}'

The response will include the wallet address. Store this for subsequent operations.

Step 2: Make Payments with fetchWithPayment

Call the thirdweb x402 fetch API directly:

# Browserbase - Create browser session
curl -s -X POST "https://api.thirdweb.com/v1/payments/x402/fetch?url=https://x402.browserbase.com/browser/session/create&method=POST" \
  -H "Content-Type: application/json" \
  -H "x-secret-key: $THIRDWEB_SECRET_KEY" \
  -d '{"browserSettings": {"viewport": {"width": 1920, "height": 1080}}}'

Step 3: Handle the Response

Success: The API returns the session data directly.

Insufficient Funds: If the wallet needs funding, the API returns:

{
  "result": {
    "message": "This endpoint requires 0.002 USDC on chain id 8453...",
    "link": "https://thirdweb.com/pay?chain=8453&receiver=0x...&token=0x..."
  }
}

When you receive a payment link, open it in the user's browser:

• If browser automation is available (MCP, browser tool, etc.), use it to navigate to the link in a new tab
• Otherwise, display the link prominently and instruct the user to open it manually

This opens thirdweb's payment page where users can fund the wallet.

API Reference

fetchWithPayment Endpoint

URL: https://api.thirdweb.com/v1/payments/x402/fetch

Method: POST

Query Parameters:

Parameter	Required	Description
url	Yes	Target API URL to call
method	Yes	HTTP method (GET, POST, etc.)
from	No	Wallet address for payment (uses default project wallet if omitted)
maxValue	No	Maximum payment amount in wei
asset	No	Payment token address (defaults to USDC)
chainId	No	Chain ID for payment (e.g., "eip155:8453" for Base)

Headers:

• x-secret-key: Your thirdweb project secret key (required)
• Content-Type: application/json

Supported x402 Services

Browserbase

x402 Endpoint: https://x402.browserbase.com
Pricing: $0.12/hour (paid in USDC on Base)

Endpoint	Method	Description
/browser/session/create	POST	Create a browser session
/browser/session/:id/status	GET	Check session status
/browser/session/:id/extend	POST	Add more time
/browser/session/:id	DELETE	Terminate session

curl -s -X POST "https://api.thirdweb.com/v1/payments/x402/fetch?url=https://x402.browserbase.com/browser/session/create&method=POST" \
  -H "Content-Type: application/json" \
  -H "x-secret-key: $THIRDWEB_SECRET_KEY" \
  -d '{"browserSettings": {"viewport": {"width": 1920, "height": 1080}}}'

Firecrawl (Non-Standard x402 - NOT RECOMMENDED)

x402 Endpoint: https://api.firecrawl.dev/v1/x402/search
Pricing: $0.01/request
Status: ⚠️ Incomplete implementation - cannot be used with thirdweb

WARNING: Firecrawl's x402 implementation is non-standard and currently unusable for automated agents:

1. Returns 401 Unauthorized instead of 402 Payment Required
2. Doesn't include payment details (payTo address, asset, amount) in response
3. Documentation says to use X-Payment: {{paymentHeader}} but doesn't explain how to generate it

Comparison with proper x402 (Browserbase):

• Browserbase: Returns 402 with x402Version, accepts, payTo, asset → thirdweb can auto-pay
• Firecrawl: Returns 401 with just {"error":"Unauthorized"} → no payment info provided

Endpoint	Method	Status
/v1/x402/search	POST	❌ Non-functional for agents

Recommended alternatives:

1. Firecrawl MCP - If available in your environment (uses standard API key)
2. Browserbase + scraping script - True x402, fully keyless
3. Standard Firecrawl API - With subscription/API key

Reference: Firecrawl x402 docs

Mail.tm (Disposable Email)

Base URL: https://api.mail.tm
Pricing: Free (no x402 payment required)

Mail.tm allows agents to create email addresses for signups and receive verification emails.

Endpoint	Method	Auth	Description
/domains	GET	No	Get available email domains
/accounts	POST	No	Create an email account
/token	POST	No	Get authentication token
/messages	GET	Yes	List all messages
/messages/:id	GET	Yes	Get full message content
/me	GET	Yes	Get account info

Create Email Account

# 1. Get available domain
DOMAIN=$(curl -s https://api.mail.tm/domains | jq -r '.["hydra:member"][0].domain')

# 2. Create account with unique address
curl -s -X POST https://api.mail.tm/accounts \
  -H "Content-Type: application/json" \
  -d '{"address": "agent-'$(date +%s)'@'"$DOMAIN"'", "password": "SecurePass123!"}'

Get Token and Check Messages

# Get auth token
TOKEN=$(curl -s -X POST https://api.mail.tm/token \
  -H "Content-Type: application/json" \
  -d '{"address": "YOUR_EMAIL", "password": "YOUR_PASSWORD"}' | jq -r '.token')

# List messages
curl -s https://api.mail.tm/messages -H "Authorization: Bearer $TOKEN"

# Read specific message
curl -s https://api.mail.tm/messages/MESSAGE_ID -H "Authorization: Bearer $TOKEN"

Important: Store email credentials (address, password, token) for later use. Consider saving to .agent-emails.json (gitignored).

Error Handling

Error	Cause	Solution
401 Unauthorized	Invalid or missing THIRDWEB_SECRET_KEY	Check environment variable
402 Payment Required	Insufficient balance	Auto-open payment link (see above)
400 Bad Request	Invalid URL or method	Verify request parameters
404 Not Found	Wrong endpoint	Check x402-specific endpoint (e.g., x402.browserbase.com)
500 Server Error	thirdweb or target API issue	Retry or check service status

Common Mistakes

1. Using wrong subdomain: api.browserbase.com vs x402.browserbase.com
2. Using wrong path: /v1/sessions vs /browser/session/create
3. Not checking for payment links: Always parse response for link field

Discovering x402 Endpoints

There are two ways to discover x402-compatible services:

Method 1: x402 Bazaar (Recommended)

The x402 Bazaar is a machine-readable catalog that helps AI agents discover x402-compatible API endpoints programmatically.

Query the Bazaar Discovery Endpoint

# Using the default facilitator (x402.org)
curl -s "https://x402.org/facilitator/discovery/resources?type=http&limit=20"

# Using CDP facilitator (Coinbase)
curl -s "https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources?type=http&limit=20"

Using the Discovery Script

# Discover available services
npx ts-node scripts/discover-services.ts

# With pagination
npx ts-node scripts/discover-services.ts --limit 50 --offset 0

# Use CDP facilitator
npx ts-node scripts/discover-services.ts --facilitator "https://api.cdp.coinbase.com/platform/v2/x402"

# Output as JSON for programmatic use
npx ts-node scripts/discover-services.ts --json

Response Format

{
  "x402Version": 2,
  "items": [
    {
      "resource": "https://x402.brows

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