Tools are callable capability wrapped with metadata. Which of the following is NOT included in a typical Tool's contract?

• A. The tool's color in the registry.
• B. Safety or usage constraints.
• C. Input and output schemas.
• D. Name and description.

Answer: (A)

The main idea is that a tool’s contract lists how to call it, what it expects, what it returns, and any rules for safe use. Safety or usage constraints ensure the tool won’t be misused or invoked in unsafe ways. Input and output schemas define the exact data shapes that the tool accepts and produces, which is crucial for correct invocation and validation. The name and description help users or agents understand what the tool does and how to use it. The color shown in the registry is purely decorative for display and organization; it doesn’t affect invocation, safety, or the interface. Therefore, the color attribute isn’t part of a typical Tool’s contract.