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

Annotations already declare idempotent=false, destructive=false, readOnly=false, but the description adds real behavioral context beyond them: it is purely additive (never removes a mark, never changes anything else) and requires the customer to be logged in. The login/auth prerequisite is exactly the kind of disclosure annotations cannot carry.

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?

Five short sentences, each carrying distinct information (purpose, add-only constraint, confirmation, identifier source, auth). Front-loaded with the action; no filler. Slightly long but nothing redundant enough to cut.

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 and a simple 3-param mutation, the description covers what matters: what it does, what it does not do, the auth requirement, and how to obtain the identifier. It never states what a successful call returns, but for a flag-setting operation with rich annotations that gap is minor.

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 description coverage is 100%, so both enum params and country are already fully documented in the schema. The description only adds where to source the sku (search_games or the ficha URL), which is marginal over the schema's own 'campo sku de search_games' text. Baseline 3 for high coverage is appropriate.

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 ('Añade un juego a la colección del cliente') plus the two possible values (owned/wanted), which is exactly the distinction that separates it from sibling tools like my_collection or search_games. An agent can tell what the tool does without opening the 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 actionable context: ask the customer for confirmation before marking, and identify the game via the sku from search_games or the game's URL. It also implicitly excludes un-marking ('no quita ninguna'), but never explicitly names when to prefer a sibling over this tool, so it stops short of a 5.

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