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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds useful behavioral details beyond the annotations: the response includes purchase links, localized 'product_urls' and 'checkout_urls' in 7 languages, and instructs the agent to select the URL matching the user's language.

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?

The description is one tightly packed sentence that front-loads the operation and then adds the necessary return-value details. There is no filler, repetition, or unnecessary background.

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 simple one-parameter retrieval tool with no output schema, the description covers what is returned (plan details plus localized purchase and checkout URLs) and how to pick the right URL. Error or not-found behavior is not mentioned, but the low complexity and annotations make this a minor 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?

The schema provides only the parameter name 'id' with no description (0% schema coverage). The description compensates by identifying it as the plan id and giving a concrete example format ('R2G-7224'), which is sufficient for a single required parameter.

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: 'Get one plan by its id', with an example id ('R2G-7224'). This clearly distinguishes it from the sibling tools list_destinations and search_plans, as it is a fetch-by-identifier operation rather than a list or search.

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?

The intended usage is implied by 'by its id': use this when you already have a plan id. However, the description does not explicitly contrast it with search_plans or list_destinations, nor does it state when not to use this tool.

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