JSON Schema validator

Valid JSON can still be the wrong data

JSON syntax only answers “can this be parsed?” JSON Schema can also say “this field must exist,” “this value must be a number,” or “this string must match a rule.” This validator checks the data against that contract.

Schema errors are useful because they are specific

A value like "20" may look like twenty to a human but it is still a string. If the schema requires a number, that difference is exactly the kind of mismatch you want to catch before the API does.

When the error list gets noisy

• Fix structural errors before chasing small value errors.
• Do not assume a third-party schema is correct just because it exists.
• For a very large schema, reduce the failing case to a smaller sample first.

A good debugging habit

Keep the schema and the smallest failing JSON side by side. One small reproducible example is usually easier to reason about than a full production payload.