Imagen astronómica del día

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds a meaningful behavioral detail beyond annotations: the default behavior of using today's date when no date is provided, which is not inferable from schema alone.

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 two short sentences, front-loaded with the core action and resource, and includes usage guidance without redundancy. Every sentence earns its place, and there is no fluff.

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 read-only tool with one optional parameter and good annotations, the description covers purpose, date parameter, and use case. It doesn't detail the return payload, but the tool is simple and self-explanatory; a return format is not critical for selection.

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?

Schema coverage is 100%, with the parameter already documented with format and default. The description reinforces the date parameter and default behavior, but adds little beyond what the schema already provides. Baseline 3 is appropriate because the schema carries the semantic load.

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 it fetches NASA's Astronomy Picture of the Day for a specific date, using a specific verb ('Trae') and resource. It distinguishes itself from sibling tools by naming APOD/photo of the cosmos for a date, which is distinct from Mars photos, asteroids, or Earth images.

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?

Explicit usage guidance is provided: 'Úsala cuando el usuario pida la imagen astronómica del día, APOD o una foto del cosmos de cierta fecha.' It gives clear context for when to use the tool, though it doesn't explicitly contrast with sibling tools or state when not to use it.

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