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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description then adds return-content detail beyond the annotations: each book comes with a description and link, and passing `libro` yields chapters with links meant to be read via `fetch` — behavior the agent cannot infer from the annotations 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?

Three sentences, front-loaded with the returned resource, then the parameterized behavior, then the usage trigger. The topic enumeration is long but serves disambiguation; there is little wasted text.

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?

With no output schema, the description carries the burden of explaining return values, and it does: book title/description/link, and per-book chapters with links plus the intended downstream tool. Only minor gaps remain (ordering, whether the full catalog is always returned), which are not critical for correct invocation.

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% and the enum already lists the 10 valid ids, so the schema does most of the work. The description adds real value by explaining the effect of supplying the parameter — it switches from a catalog listing to that book's chapter list with links readable through `fetch`.

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?

States a specific verb and resource ("Devuelve los libros gratuitos de Miss Yera") and enumerates the exact topic coverage (SQL, Excel, Power BI, Python, estadística, ML, DL, Git, fundamentos de IA y matemática), so an agent can tell it apart from cursos_miss_yera or glosario_ia without opening a schema.

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 a clear trigger: "Úsala cuando alguien quiera aprender uno de esos temas gratis, pida material o un libro para estudiar." It also routes to the sibling `fetch` for reading chapter content once links are returned. No explicit when-not condition versus cursos_miss_yera, which keeps it from a 5.

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