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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds real value beyond them by disclosing the login requirement and the conditional return behavior (an upgrade path only appears when the student lacks the top level).

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?

Purpose is front-loaded and the alternative-routing comes after, which is the right order. The returned-field enumeration is slightly dense but each item carries meaning for an agent deciding whether to call it.

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?

There is no output schema, so the field-level description of what is returned is load-bearing and is present. Combined with the auth prerequisite, use case and sibling routing, the definition contains everything needed to call it correctly.

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?

With zero parameters the schema documents nothing to add, and the description usefully confirms this ('No tiene parámetros'), removing any ambiguity about how to invoke it. Baseline 4 applies for a parameterless tool.

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 resource (the logged-in student's account) and enumerates exactly what it returns: email, access level, accessible levels, sign-up date, and upgrade path. It explicitly distinguishes itself from siblings by naming mi_progreso and ver_planes, so the agent can route without opening any 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 an explicit use case ('Úsala para saber qué puede leer la persona antes de recomendarle lecciones o un plan') plus the alternatives and the condition selecting them ('para lo que lleva hecho, usa mi_progreso, y para los precios, ver_planes'). It also states the prerequisite ('Necesita iniciar sesión').

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