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

No annotations are provided, so the description carries the full transparency burden. It discloses that the tool returns plans with specific fields (sku, data amount, validity days, USD price, coverage carriers) and notes that all prices are in USD. This is adequate for a read-oriented search tool, but it does not discuss rate limits, auth requirements, or potential side effects.

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 concise: three sentences, each serving a distinct purpose (purpose, filters, return fields). Information is front-loaded with the primary action. No unnecessary words or repetition.

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?

Given the tool has 3 optional parameters and no output schema, the description covers the essential aspects: what it searches, filters, and returns. It mentions the return fields and price currency. It could be more complete by noting ordering or pagination behavior, but it is sufficient for a simple search tool.

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 the baseline is 3. The description adds value by providing concrete examples for the country slug ('japan', 'usa', 'europe') and stating 'Omit to list all', which clarifies behavior beyond the schema. The region enum is also hinted at, though the schema already defines it.

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 'Search Alt eSIM travel data plans' with a specific verb and resource. It lists filter options and return fields, making the purpose clear. However, it does not explicitly differentiate from sibling tools like 'list_destinations' or 'get_esim_plan', which would strengthen clarity.

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 provides context on what to filter by (country slug, region, max price) and gives examples ('japan', 'europe'). It implies usage for finding plans but does not give explicit guidance on when to use this tool versus alternatives, nor does it mention when not to use it.

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