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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavioral context: results are ranked neutrally rather than by sponsorship, each result carries a buy_url and a price-check timestamp. It does not state what happens on an unrecognized country or how truncation by limit is signaled.

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?

Three sentences, all load-bearing: scope and ranking first, filter dimensions second, return-value shape last. No repetition of the title and no 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?

With 10 parameters and no output schema, the description usefully discloses the key return fields (buy_url, last-checked time) and the ranking model. Remaining gaps are minor but real: default result count, behavior on an unknown destination, and empty-result semantics are left to the schema or unspecified.

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's meaning is already documented. The description only restates the filter categories and sort options at a high level, adding no syntax, default, or edge-case detail beyond the schema. Baseline 3 is appropriate when the schema carries the full load.

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 (find travel eSIM data plans), the scope (every provider esimdata tracks), and the ranking model (neutral, price / price-per-GB / validity). This makes it clearly distinguishable from siblings like compare_plans, country_overview and get_plan, which operate on a narrower or already-selected set.

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 a clear picture of when this tool fits: destination-based discovery with filtering by trip length, data, unlimited, needs and budget. However, it never explicitly contrasts with compare_plans or country_overview, so an agent must infer which sibling to pick for a comparison or an overview.

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