The short version
When two systems need to exchange information, they need a shared format. JSON (JavaScript Object Notation) is that format for most of the modern web. It's what your weather app gets back when it asks an API for the forecast. It's what a webhook sends when a payment goes through. It's what MCP servers use to describe their tools.
Despite the name, JSON has nothing to do with writing JavaScript. It's just a text format that happened to borrow its syntax from there.
How it works
JSON organises data into two structures:
- Objects are collections of key-value pairs, wrapped in curly braces. Each key is a string, each value can be a string, number, boolean, null, another object, or an array.
- Arrays are ordered lists, wrapped in square brackets.
{
"name": "Claude",
"type": "LLM",
"released": 2024,
"capabilities": ["text", "code", "analysis"],
"open_source": false
}
That's valid JSON. A person can read it. A machine can parse it. The keys describe what each piece of data is, and the values hold the actual data.
A few rules: keys must be in double quotes. No trailing commas. No comments. It's strict, which is what makes it reliable for machine-to-machine communication.
Why it matters
If you use any API, any webhook, any automation tool, you'll encounter JSON. Zapier shows it in debug views. Airtable's API returns it. Claude's responses are wrapped in it. Being able to read a JSON object and understand its structure means you can debug integrations, write better prompts, and understand what's actually happening when tools talk to each other.