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 value by specifying the return format (country name + code + cheapest plan price in EUR), which is useful for an agent to know what to expect, especially since there is no output schema. It doesn't describe edge cases like empty lists, but for a simple read-only listing tool this is sufficient.

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 a single, focused sentence that leads with the action and resource, then clarifies the output contents in a parenthetical. Every word earns its place; there is no redundancy or filler.

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, read-only tool with no output schema, this description tells the agent exactly what it returns and the fields included. It covers all necessary information to call the tool correctly and interpret the result. Nothing essential is missing for 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?

There are zero parameters, and the input schema is empty. The description does not need to explain any parameters, and it correctly avoids repeating anything about the schema. Per the baseline rule for 0 parameters, a score of 4 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?

The description clearly states the verb ('List') and the resource ('all destinations'), and specifies the exact fields returned (country name, code, cheapest plan price in EUR). This distinguishes it from siblings like get_plan (which likely retrieves a single plan) and search_plans (which searches plans), so an agent can immediately tell when to use it.

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 description gives no guidance on when to choose this tool over alternatives. It simply states what it does; it does not mention when to use it (e.g., 'when you need a full list of destinations') or when not to use it, nor does it reference siblings or any prerequisites.

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