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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered structurally. The description adds that each fit carries full plan facts, total price and a one-sentence reason 'built only from catalogue facts' — useful grounding context — but does not disclose latency, result caps beyond 'up to three', or how budget/currency affect filtering 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?

Two sentences, front-loaded with the transformation and what comes back, with no filler. The second sentence is dense but every clause (facts, total price, grounded reason) 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?

With a full output schema and annotation coverage, the description only needs to convey purpose and routing, which it does. The remaining gap is minimal — it doesn't mention what happens when budget/currency/language conflict with bucket, but the schema handles precedence.

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 100%, so every parameter including the usage enum, bucket, currency and gb_per_day override is fully documented inline. The description restates countries/days/usage at a high level with no added syntax or precedence detail, so it neither adds nor detracts; baseline 3 applies.

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 gives a specific verb+resource ('Turn a trip into up to three plan recommendations') and enumerates the inputs that drive the recommendation (countries, days, data usage). It also distinguishes itself from the list-oriented sibling search_esim_plans by framing itself as the trip-description entry point.

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 gives an explicit routing rule: 'Use this first whenever the user describes a trip rather than asks for a list,' which implicitly contrasts with search_esim_plans. However, it does not name the sibling tools (get_plan_details, search_esim_plans) or state what to do once a recommendation is returned, so the routing is clear but not exhaustive.

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