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

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Prerequisites

Before using this skill, ensure:

1. 1. THIRDWEBSECRETKEY 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	INLINECODE0	INLINECODE1	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):

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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:

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Step 3: Handle the Response

Success: The API returns the session data directly.

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

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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: INLINECODE9

Method: POST

Query Parameters:

Parameter	Required	Description
INLINECODE10	Yes	Target API URL to call
INLINECODE11

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)
• INLINECODE17: application/json

Supported x402 Services

Browserbase

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

Endpoint	Method	Description
INLINECODE19	POST	Create a browser session
INLINECODE20

GET | Check session status |
| /browser/session/:id/extend | POST | Add more time |
| /browser/session/:id | DELETE | Terminate session |

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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. 1. Returns 401 Unauthorized instead of INLINECODE25
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
INLINECODE32	POST	❌ Non-functional for agents

Recommended alternatives:

1. 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
INLINECODE34	GET	No	Get available email domains
INLINECODE35

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

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Get Token and Check Messages

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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 THIRDWEBSECRETKEY	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. 1. Using wrong subdomain: api.browserbase.com vs INLINECODE43
2. Using wrong path: /v1/sessions vs INLINECODE45
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

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Using the Discovery Script

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Response Format

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Query Parameters

Parameter	Type	Default	Description
INLINECODE47	string	-	Filter by protocol type (e.g., "http")
INLINECODE49

number | 20 | Number of resources to return (max: 100) | | offset | number | 0 | Offset for pagination |

Method 2: Manual Discovery

When encountering a new service that might support x402:

1. Check for x402 Subdomain

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2. Check for /x402/ Path Prefix

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3. Test for 402 Response

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Expected for true x402:
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If you see 401 Unauthorized: The service uses hybrid x402 (needs API key + payment).

4. Check Service Documentation

Look for x402/payments documentation:

• - INLINECODE51
• INLINECODE52
• Search for "x402" or "402" in their docs

Additional Resources

• - See references/API-REFERENCE.md for complete API documentation
• See references/SERVICES.md for x402-compatible service examples

Links

• - x402 Protocol
• x402 Bazaar Discovery
• thirdweb x402 Documentation
• Browserbase x402 Docs