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

Annotations already declare this as a safe, open-world, non-destructive read, so the safety profile is covered. The description adds a list of the retrieved fields (throttle behaviour, daily reset, coverage list, reviews), which is useful scope information beyond the annotations, but it discloses nothing about latency, pagination, or failure modes.

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?

Single front-loaded sentence that names the resource first and then quantifies the returned fields with no filler. Slightly dense as one continuous clause list, but every phrase 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 an output schema present, the description need not explain return values, and annotations cover the safety profile; the schema documents both parameters fully. What remains is the workflow tie to search_esim_plans, which is only implied, leaving a small gap.

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 are already fully documented, including the language localisation effect on names and link currency. The description only references product id and adds no syntax, format, or edge-case meaning beyond the schema, matching the baseline for high-coverage schemas.

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 ('Full details for one e-eSIM plan by product id') and enumerates exactly what is returned, so an agent knows it is a single-record fetch. However, it never names or contrasts itself with the sibling search_esim_plans, which is the closest alternative, so sibling differentiation is only implicit.

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 product id hint ('WooCommerce product id from search_esim_plans') implies the tool follows a search step, giving implied usage. There is no explicit when-to-use statement, no exclusions, and no direct comparison against search_esim_plans or start_checkout.

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