What’s JSON Schema For in Claude API Tools Exactly?
JSON schema tells Claude your tool’s expected arguments and structure for accurate calls—not for responses or storage—core to Claude API tool integration mastery.
Question
What is the main purpose of a JSON schema when working with Claude tools?
A. To format the final response for users
B. To tell Claude what arguments your function expects and how to use it
C. To store the results of tool function calls
D. To encrypt data between Claude and your server
Answer
B. To tell Claude what arguments your function expects and how to use it
Explanation
The main purpose of a JSON schema in Claude tools is to define the exact structure, parameters, types, descriptions, and constraints for a tool’s input arguments (e.g., {“name”: “get_weather”, “inputSchema”: {“type”: “object”, “properties”: {“city”: {“type”: “string”}}}}), enabling Claude to understand, validate, and correctly populate function calls during generation without trial-and-error. This schema acts as the model’s interface documentation, ensuring precise tool usage in multi-turn conversations, unlike final response formatting (A, handled separately), result storage (C, post-execution), or encryption (D, unrelated to schema).