📶HTTP Status Codes Database
Reference database of HTTP response status codes with phrase, category and explanation. Look up a specific code or list a whole category (1xx–5xx).
Worked examples
What is HTTP 402?
GET /api/v1/dev/http-status-codes?code=402
Result: 402 Payment Required
All client errors
GET /api/v1/dev/http-status-codes?category=client-error&limit=20
Result: 15 status codes — 4xx Client Error
What is 301?
GET /api/v1/dev/http-status-codes?code=301
Result: 301 Moved Permanently
Machine API (x402)
$0.001 / callThis tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.
GET /api/v1/dev/http-status-codes?code=402 HTTP/1.1
Host: agenttools-hub.vercel.app
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "dev/http-status-codes",
"input": {"code":402},
"result": { "value": 402, "answer": "402 Payment Required" }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
Every HTTP response starts with a three-digit status code: 1xx informational, 2xx success, 3xx redirect, 4xx client error, 5xx server error. Look up any code — including 402 Payment Required, the code the x402 protocol revived for machine-to-machine payments.
Frequently asked questions
What is the difference between 401 and 403?
401 means 'who are you?' — authenticate first. 403 means 'I know who you are and you still can't do this'.
Is 402 Payment Required actually used?
Historically reserved, now actively used by the x402 protocol: APIs return 402 with payment requirements and AI agents pay USDC before retrying.