👨‍💼 As we add more features, it's inevitable that things will sometimes go wrong—maybe a user tries to get information that doesn't exist, or there's a problem saving data. It's important that both users and LLMs get clear, structured feedback when errors happen.

Example error response:

{
	"jsonrpc": "2.0",
	"id": 2,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "Entry with id 123 not found"
			}
		],
		"isError": true
	}
}

Luckily for us, the MCP TypeScript SDK handles errors automatically. So all you need to do is throw an error from your tool, and the SDK will handle the rest!

For this step, we're going to say that the second number cannot be negative. If it is, throw an error with a descriptive message and then try it out in the inspector. You'll notice the isError field is set to true and the content is the helpful error message you provided.