First-pass JSON validation: test syntax and one schema rule

Before checking a large payload, validate a harmless small object that includes a required field, nested value, and a deliberately wrong type. Confirm that the validator catches malformed syntax and that a separate schema check rejects the type error. Then use the same rules on real data, keeping private values out of untrusted tools. This first pass establishes what the validator actually checks; a green syntax indicator alone says nothing about application-specific requirements.