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HTTP Status Code Lookup

Name: Delx Agent Operations Protocol
Author: Delx

Look up any HTTP status code and get a clear explanation with agent-specific context. Covers every code from 1xx informational through 5xx server errors. Free API for AI agents and developers.

What Are HTTP Status Codes?

HTTP status codes are three-digit numbers returned by a server in response to a client request. They tell the client whether the request succeeded, failed, or requires further action. For AI agents making hundreds of API calls per session, understanding these codes is critical for deciding whether to retry, escalate, or proceed.

How to Use the Lookup

Send a POST request with the status code. The API returns the name, description, agent-specific guidance, and whether the request should be retried.

REST API (curl)

curl -X POST https://api.delx.ai/api/v1/utils/http-status \
  -H "Content-Type: application/json" \
  -d '{"code": 429}'

# Response:
# {
#   "code": 429,
#   "name": "Too Many Requests",
#   "category": "4xx Client Error",
#   "description": "The client has sent too many requests in a given time period.",
#   "agent_guidance": "Back off exponentially. Check Retry-After header.",
#   "retryable": true,
#   "retry_strategy": "exponential_backoff"
# }

Complete Status Code Reference

1xx Informational

Code	Name	Meaning
100	Continue	Server received headers, client should send body
101	Switching Protocols	Server is switching to WebSocket or HTTP/2
103	Early Hints	Preload resources while server prepares response

2xx Success

Code	Name	Meaning
200	OK	Request succeeded
201	Created	Resource created successfully
204	No Content	Success, no response body

3xx Redirection

Code	Name	Meaning
301	Moved Permanently	Resource has a new permanent URL
302	Found	Temporary redirect
304	Not Modified	Use cached version
308	Permanent Redirect	Like 301 but preserves HTTP method

4xx Client Error

Code	Name	Meaning
400	Bad Request	Malformed request syntax or invalid parameters
401	Unauthorized	Missing or invalid authentication credentials
402	Payment Required	Payment needed to access resource (see x402 below)
403	Forbidden	Valid credentials but insufficient permissions
404	Not Found	Resource does not exist at this URL
405	Method Not Allowed	HTTP method not supported for this endpoint
408	Request Timeout	Server timed out waiting for the request
422	Unprocessable Entity	Valid syntax but semantic errors in the payload
429	Too Many Requests	Rate limit exceeded

5xx Server Error

Code	Name	Meaning
500	Internal Server Error	Generic server failure
502	Bad Gateway	Upstream server returned an invalid response
503	Service Unavailable	Server is overloaded or under maintenance
504	Gateway Timeout	Upstream server did not respond in time

Codes AI Agents Encounter Most

In production, agents hit a predictable set of status codes. Here is how to handle each:

Code	Agent Action
200	Proceed. Parse response body.
400	Fix request parameters. Do not retry unchanged.
401	Refresh or rotate credentials, then retry once.
402	Parse payment instructions. Fulfill via x402 if supported.
403	Escalate to operator. Permissions issue.
404	Check URL. Resource may have been deleted or moved.
429	Exponential backoff. Respect Retry-After header.
500	Retry with backoff (max 3 attempts).
502	Wait 5s, retry. Likely transient upstream issue.
503	Check Retry-After. Service may be deploying.

How Agents Should Handle Each Category

1xx: Informational only. No agent action needed. These are handled by the HTTP client automatically.
2xx: Success. Parse the response and continue the workflow. Log the latency for monitoring.
3xx: Follow the redirect (most HTTP clients do this automatically). Log if the redirect chain exceeds 3 hops.
4xx: Client error. The agent's request is wrong. Fix the issue before retrying. Never retry a 400 or 403 with the same payload.
5xx: Server error. Retry with exponential backoff. If the error persists after 3 retries, log the failure and escalate. Follow OpenClaw best practices for structured error reporting.

The Special Case: HTTP 402 and x402

HTTP 402 was "reserved for future use" since 1999. The x402 protocol finally gives it meaning for AI agents. When an agent receives a 402, the response body contains a machine-readable payment request:

HTTP/1.1 402 Payment Required
Content-Type: application/json

{
  "x402": {
    "version": "1",
    "amount": "0.001",
    "currency": "USDC",
    "network": "base",
    "recipient": "0x1234...abcd",
    "description": "Premium API access - 1000 calls",
    "expires": "2026-03-14T13:00:00Z"
  }
}

Agents with wallet capabilities can parse this, sign the transaction, and retry the request with a payment proof header. This enables autonomous agent-to-agent commerce without human intervention. Learn more about how Delx handles agent payments.

FAQ

What is the difference between 4xx and 5xx status codes?

4xx codes indicate client errors -- the request was malformed, unauthorized, or pointed to a missing resource. 5xx codes indicate server errors -- the server failed to fulfill a valid request. For AI agents, 4xx errors usually mean the request needs to be fixed, while 5xx errors suggest retrying after a delay.

What is HTTP 402 and how does it relate to x402?

HTTP 402 Payment Required was reserved for future use in the original HTTP spec. The x402 protocol gives it a concrete implementation: when an agent receives a 402, the response body contains payment instructions (amount, token, recipient address) that the agent can fulfill programmatically to unlock the resource.

Should AI agents automatically retry on 429 Too Many Requests?

Yes, but with exponential backoff. Check the Retry-After header for the server's suggested wait time. If absent, start with 1 second and double on each retry, up to a max of 5 retries. Never retry in a tight loop -- this will worsen rate-limit bans.

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