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

No annotations are provided, so the description carries the full burden, and it does disclose the return shape (countries per area, plan count, cheapest total price) plus the important semantic caveat that countries_on_some_plans may not be covered by every plan. It stops short of stating pagination, auth, or rate-limit behavior, but the substantive behavioral risks are covered.

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?

Front-loaded with purpose and examples, then workflow, then the sibling disambiguation last. Dense but nearly every clause carries actionable information; the country-example list is slightly verbose but aids recognition.

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 no annotations, the description must explain returns and usage, and it does both: it enumerates the returned fields, clarifies the countries vs countries_on_some_plans distinction, and links to the downstream tools needed to act on the result.

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 parameters (country, currency) are already documented in the schema and the description adds nothing about them. The references to `coverage` and `countries` belong to sibling tools, not this tool's inputs. Baseline 3 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 ('List every multi-country coverage area Siima sells') and immediately scopes it with concrete examples ('Europe+', 'South East Asia', 'CENAM') plus worldwide plans. It also names what each result contains, so an agent can distinguish it from list_destinations at a glance.

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?

Explicit when-to-use ('Use this for a trip crossing several countries'), explicit routing to the alternative ('For a single-country trip use list_destinations instead'), and a follow-up workflow with search_esim_plans and get_esim_plan. This is a complete decision path.

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