Fotos de rovers en Marte

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive nature, lowering the bar. The description adds valuable behavioral context: if no sol/date is provided, it returns the most recent photos. This goes beyond schema and annotations, though it does not detail rate limits or response format.

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 three sentences, front-loaded with the main purpose, followed by filtering options and a usage tip. Every sentence contributes valuable information without redundancy or filler.

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 photo-fetching tool, the description covers essential aspects: purpose, filters, default behavior, and when to use it. Although there is no output schema, the description's mention of 'fotos' implies the return type. Minor gaps like response format details are acceptable given the tool's simplicity.

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%, so the baseline is 3. The description adds meaning by explaining that sol and fecha_terrestre are filters and that omitting them returns the most recent photos. This clarifies the interaction between parameters beyond the schema definitions.

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 the tool's purpose: fetching Mars rover photos from Curiosity, Opportunity, Spirit, and Perseverance. It specifies the resource (Mars rovers) and distinguishes it from sibling tools (APOD, asteroids, Earth images) by focusing on Mars rover photos.

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?

The description provides explicit usage guidance: 'Úsala cuando pidan fotos de Marte o de un rover.' It clearly indicates when to use the tool, though it does not explicitly mention when not to use it or list alternatives. However, the sibling tools are clearly distinct in function, so this is sufficient.

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