Test webhook endpoints -- send POST/PUT/PATCH/DELETE with custom headers and payloads. Measure latency and TLS. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

json

{
  "mcpServers": {
    "webhook-tester": {
      "url": "https://webhook-tester.api.klymax402.com/mcp"
    }
  }
}

Quickstart -- HTTP (x402)

bash

curl -X POST "https://webhook-tester.api.klymax402.com/api/test" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com"}'
# -> 402 Payment Required, with an x402 payment challenge in the response body

Any x402-aware client (@x402/fetch, x402-agent-tools, ATXP) handles the 402 -> sign -> retry cycle automatically.

Tools

Tool	Method	Path	Price	Description
`api_test_webhook`	POST	`/api/test`	$0.005	Send a test request to a webhook URL and analyze the response

`api_test_webhook`

Use this when you need to test a webhook endpoint by sending a request with custom headers, body, and method. Returns full response data in JSON.

Parameters

Name	Type	Required	Description
`url`	string	yes	Webhook URL to test (must be https)
`method`	string	no	HTTP method: POST, PUT, PATCH, DELETE (default: POST)
`headers`	object	no	Custom headers as key-value pairs
`body`	object	no	JSON body to send
`timeout`	number	no	Timeout in seconds (default: 10, max: 30)

Example response:

json

{"url":"https://hooks.example.com/callback","method":"POST","statusCode":200,"responseBody":{"received":true},"latency":142,"tlsInfo":{"protocol":"TLSv1.3","cipher":"AES-256-GCM"},"requestSize":256,"responseSize":48}

When to use: testing webhook integrations, debugging API callbacks, validating endpoint availability, and measuring webhook response times.

Not for: web scraping (use web_scrape_to_markdown), screenshot capture (use capture_screenshot), HTTP header security audit (use network_analyze_headers).

Example agent prompts

"Test a webhook endpoint by sending a request with custom headers, body, and method"

Payment

Protocol: x402 -- HTTP-native pay-per-call, no signup, no API key
Network: Base L2 (eip155:8453)
Asset: USDC
Facilitator: Coinbase CDP (primary), PayAI (fallback)
Also reachable via ATXP (OAuth-wrapped x402, RFC 9728 protected-resource metadata)