64 services carry this tag in their source record. Tags come from the provider, not from us — a tag is a claim about what the service does, not proof that it does it well.
HTTP 401 Unauthorized: what it means (authentication required or failed), what a client should do (authenticate (see WWW-Authenticate)), the class it belongs to, whether it is retryable and idempotency-safe, the defining...
HTTP 402 Payment Required: what it means (x402: pay to access (PAYMENT-REQUIRED header)), what a client should do (sign the payment and retry), the class it belongs to, whether it is retryable and idempotency-safe, the d...
HTTP 403 Forbidden: what it means (authenticated but not allowed), what a client should do (do not retry without new rights), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and c...
HTTP 404 Not Found: what it means (no such resource), what a client should do (check the URL), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-code...
HTTP 405 Method Not Allowed: what it means (method not supported here), what a client should do (see Allow header), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common caus...
HTTP 406 Not Acceptable: what it means (cannot satisfy Accept headers), what a client should do (relax Accept), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes....
HTTP 407 Proxy Authentication Required: what it means (authenticate to the proxy), what a client should do (send Proxy-Authorization), the class it belongs to, whether it is retryable and idempotency-safe, the defining R...
HTTP 408 Request Timeout: what it means (server gave up waiting), what a client should do (retry), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-c...
HTTP 409 Conflict: what it means (state conflict (e.g. edit collision)), what a client should do (refresh and retry), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common ca...
HTTP 410 Gone: what it means (permanently removed), what a client should do (delete references), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-cod...
HTTP 411 Length Required: what it means (Content-Length missing), what a client should do (add Content-Length), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes....
HTTP 412 Precondition Failed: what it means (If-* condition false), what a client should do (refresh ETag and retry), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common ca...
HTTP 413 Content Too Large: what it means (body exceeds limit), what a client should do (shrink or chunk), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Preci...
HTTP 414 URI Too Long: what it means (URL exceeds limit), what a client should do (use POST), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-code r...
HTTP 415 Unsupported Media Type: what it means (Content-Type not accepted), what a client should do (change the encoding), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and comm...
HTTP 416 Range Not Satisfiable: what it means (range outside the resource), what a client should do (fix Range), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes....
HTTP 417 Expectation Failed: what it means (Expect header not met), what a client should do (drop Expect), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Preci...
HTTP 418 I'm a teapot: what it means (April-fools RFC; used to reject bots), what a client should do (stop), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Pre...
HTTP 421 Misdirected Request: what it means (wrong server/connection), what a client should do (reconnect), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Prec...
HTTP 422 Unprocessable Content: what it means (well-formed but semantically invalid), what a client should do (fix the fields), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and...
HTTP 423 Locked: what it means (WebDAV: resource locked), what a client should do (wait/unlock), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-cod...
HTTP 424 Failed Dependency: what it means (WebDAV: earlier action failed), what a client should do (fix dependency), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common cau...
HTTP 425 Too Early: what it means (replay risk with 0-RTT), what a client should do (retry later), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Precise one-c...
HTTP 426 Upgrade Required: what it means (switch protocol (see Upgrade)), what a client should do (upgrade), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes. Pre...