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

Annotations already cover read-only, idempotent, non-destructive and open-world behavior, so the description adds meaningful context instead: prices are denominated in USD, no order or payment is created, and country-only results should be preferred over regional bundles. It stops short of describing result size, pagination, or what a plan record contains.

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?

Four short sentences with zero padding: the core purpose, the currency, the preference ordering, and the side-effect disclaimer each occupy one clear clause. Front-loaded and easy to scan.

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 five optional filters, no output schema, and no parameter descriptions, the definition leaves the shape of results undefined (fields per plan, ordering, how de-duplication of country vs. regional bundles works). For a read-only search tool this is workable but not complete.

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 0%, so the description must carry parameter meaning. It clarifies the two-letter ISO format for country_code and the USD currency for max_price_usd, but says nothing about limit, min_data_gb, or min_validity_days; it relies on those names being self-explanatory.

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?

"Find prepaid travel eSIM data plans by two-letter ISO destination code" gives a specific verb (find) and resource (eSIM data plans) plus the keying dimension. The closing line "No order or payment is created" implicitly separates it from get_checkout_link, but the distinction from get_plan (search vs. single-plan retrieval) is never made explicit.

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?

Usage context is implied by the required destination code, and "Country-only plans are preferred; regional bundles are a fallback" guides result interpretation. However, there is no statement of when to call this versus get_plan or get_checkout_link, and no prerequisites or sequencing guidance.

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