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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false). The description adds real behavioral context beyond them: results are returned cheapest-first, and the destination can be a country, a region, or global. It still omits result limits or pagination behavior.

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?

A single sentence with zero waste: verb+resource first, then scope, then sort order, then filter options. Nothing is repeated from the title or schema and every clause carries information.

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 6-parameter search tool with 17% schema coverage and no output schema, the description leaves gaps: result shape, result count/pagination, and the unit/currency meaning of the numeric filters are unaddressed. The cheapest-first ordering and destination granularity are useful, but not enough to be fully self-contained.

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 coverage is only 17% (only locale is documented), so the description must compensate. It partially does by naming the filter dimensions — price, data, validity, unlimited — which map to maxPrice, minDataGB, maxValidityDays and unlimited, but it adds no units, currency semantics, or confirmation that destination is required.

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 ('Search the eSIM plans'), names the scope of the destination (country, region or global), and discloses the sort order and filter dimensions. It is clearly distinguishable from get_plan, but it never explicitly names or contrasts with the siblings (recommend_plan, list_destinations).

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 implies the usage context (search plans for a destination with optional filters) but gives no explicit when-to-use guidance, no exclusions, and no mention of how it relates to alternatives like recommend_plan or get_plan. An agent must infer the routing decision entirely.

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