What is a JSON?

Despite the name, JSON has become language-agnostic: every mainstream programming language ships a parser and serializer for it, which is why it dominates as the wire format for REST APIs, webhooks, and configuration files. Its syntax is deliberately small — objects in curly braces, arrays in brackets, strings, numbers, booleans, and null — so a parser can be written in a few hundred lines and a human can read a payload without a schema reference open in another tab. That readability comes at a cost: JSON has no native way to express dates, binary data, or comments, so systems layer conventions like ISO 8601 strings or base64 encoding on top. For AI agents and tool-calling systems, JSON is the default format for both function arguments and function results because large language models are heavily trained on it and can reliably produce syntactically valid output when constrained with a schema.