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

Annotations only declare readOnlyHint and openWorldHint; the description adds the operationally important behavior: the output is a personal single-use link valid for 30 minutes, and the user completes the upload on that page rather than the agent doing it. It also front-loads the mandatory prerequisite skill call, which is the kind of sequencing an agent cannot infer from schema or annotations.

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?

Front-loaded with the mechanism, then the when-to-use rule, the alternative, and the prerequisite in a compact three-part structure. The first sentence is long and heavily nested in Spanish, which slows parsing slightly, but no sentence is 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 zero-parameter tool with no output schema, it covers the flow, the expiry constraint, the accepted file types, the sibling alternative, and the prerequisite call — effectively describing the return value (a link). It does not describe what happens after the user finishes (confirmation, partial imports, failures), which is the only remaining gap.

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?

There are zero input parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly does not invent parameters, and instead spends its budget on flow and prerequisites.

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?

Names a specific action (importar subrayados de Kindle) and explains the actual mechanism: it hands back a personal single-use 30-minute link to a page where the user uploads My Clippings.txt or the emailed notebook and picks which books go to their brain. That mechanism detail makes it unmistakable versus siblings like save_highlights or read_book.

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?

Gives an explicit trigger ('Úsala cuando quiera importar sus subrayados, notas o highlights de Kindle'), an explicit alternative with the condition that selects it ('si los lees tú en su navegador, usa save_highlights'), and a prerequisite step ('Antes, carga la skill subrayados-kindle con get_skill'). Routing is fully determined.

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