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

With no annotations, the description carries the full disclosure burden and does state that the operation is read-only ('Solo lectura') and what the list represents. It does not mention ordering, pagination, or what is returned when the user has no friends, which are the remaining behavioral gaps for a list tool.

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?

Two short sentences with no wasted wording: the resource and returned fields come first, followed by the read-only constraint and the redirect for mutations. Nothing repeats the name or pads the 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?

For a zero-parameter list tool with no annotations and no output schema, the description covers purpose, return fields, read-only status, and where mutations happen. Only secondary details such as pagination or result limits are missing, which is minor 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?

The tool takes zero parameters, so the baseline is 4. The description adds value by describing the shape of each returned item ({id, name, email}), effectively compensating for the absence of an output schema, though it does not describe parameter behavior because there is none.

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 states a specific verb and resource ("Lista los amigos del usuario") and even names the fields returned ({id, name, email}), plus the functional meaning of the list (the only people one can share with). That is enough to distinguish it from the many *_list siblings 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?

It explicitly scopes usage to a read-only listing and states where the mutating counterparts live (invitar, aceptar, dejar de ser amigos → web, Ajustes → Amigos). An agent knows both when to call this and where not to look for friend mutations.

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