apod

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are present. The description only states the key requirement and the general return value; it does not disclose whether the operation is read-only, what errors may occur, or any rate-limit/network behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single concise sentence with no redundant or unnecessary content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple APOD-fetching tool, the description is minimally adequate, but it lacks important context such as date format, expected response contents, and failure behavior, especially given the absence of annotations.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The date parameter is implied to be optional and to specify a particular day, but the accepted format (e.g., YYYY-MM-DD), valid date range, and behavior when omitted are not described.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states that the tool returns NASA's Astronomy Picture of the Day for today or a specified date, using an unambiguous verb ('返す') and a specific resource. This distinguishes it from the sibling tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It mentions the NASA_API_KEY requirement, which is useful, but it does not explain when to prefer this tool over siblings or provide guidance on date formatting or invocation context.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.