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API Payload Doctor

Paste an API request or response and get a structured diagnosis of what could go wrong with it.

EngineeringBackendAPI
🔒Your tool inputs are processed in your browser and are not uploaded or sent to analytics.

Paste an API response and find structural problems. Start with the small example below, or replace it with your own JSON.

Example data is fictional. Payloads stay in browser memory; they are not saved or sent.

Target: Web (~97.7 KB guideline)
Result
Inconsistent key casing
Why it matters
Found snake_case, camelCase mixed in the same payload. Consumers often assume one convention — pick one (e.g. camelCase) and stick with it.
Action
Pick one convention (camelCase is the most common for JSON APIs) and normalize every key to it.
Details: all checks and size breakdown
Payload size
187 B
Issues found
3
Checks run
6

Size breakdown by top-level key

items61.4% · 51 B
displayName16.9% · 14 B
signupDate14.5% · 12 B
avatar4.8% · 4 B
user_id2.4% · 2 B
#1 items · 51 B#2 displayName · 14 B#3 signupDate · 12 B#4 avatar · 4 B#5 user_id · 2 B

Estimated from each top-level value's own JSON size — structural characters like braces and commas aren't split out, so treat this as a close approximation, not an exact byte count.

✓
Valid JSON
The payload parses without errors.
✓
Payload size: 187 B
Comfortably under the ~97.7 KB guideline for a Web target.
⚠
Inconsistent key casing
Found snake_case, camelCase mixed in the same payload. Consumers often assume one convention — pick one (e.g. camelCase) and stick with it.
ℹ
1 field explicitly null
avatar — make sure your consumer distinguishes "null" from "missing" if that matters to you.
⚠
1 ambiguous date-like value
signupDate: "03/04/2024" — formats like "03/04/2024" are read as MM/DD in the US and DD/MM almost everywhere else. Use ISO 8601 (YYYY-MM-DD) instead.
⚠
Inconsistent array item shapes
items: items have 2 different key sets
Advanced: upload a file, target context, traffic estimate
What this tool does and why

Before you start

What

Paste an API request or response and get a structured diagnosis of what could go wrong with it.

Why

It exposes structural issues such as inconsistent keys, ambiguous fields, unsafe dates, oversized bodies, and deep nesting before they become integration failures.

Your Result and Action update in the tool as you change its inputs.

Model note

This browser-side model explains the inputs you choose. Check an important decision against the real system, brief, or production constraints.

Save this tool and explore next steps
My Toolooo
Saved only in this browser.
How this tool stays honest

How it works

Drop in a JSON payload and API Payload Doctor runs it through a checklist real backend engineers use — inconsistent key casing, ambiguous null vs. missing fields, oversized payloads, unsafe date formats, duplicate keys, and deep nesting that will bite you later. Every finding is explained, not just flagged.

Assumptions

The tool runs in your browser and models the information you provide. It does not know facts outside that model.

Limitations

The diagnosis uses structural and consistency checks on the pasted JSON. It does not call the API, execute a schema, test authorization, or prove how a server will process the payload.

Understand API Payload Doctor

What this tool helps you understand

Drop in a JSON payload and API Payload Doctor runs it through a checklist real backend engineers use — inconsistent key casing, ambiguous null vs. missing fields, oversized payloads, unsafe date formats, duplicate keys, and deep nesting that will bite you later. Every finding is explained, not just flagged.

When to use it

When diagnosing a request or reviewing a response contract change.

Try a scenario

Compare an expected object with one that omits a field and another that supplies null. Follow the affected path and confirm what the consumer permits.

How to read the result

Read each finding as a diagnostic signal, then confirm it against the contract, system, file, or production context you actually control.

Assumptions and limits

The diagnosis uses structural and consistency checks on the pasted JSON. It does not call the API, execute a schema, test authorization, or prove how a server will process the payload.

Toolooo is part of Khizooology, created byKhizar Imtiaz (khizooo).