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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds useful behavior (result ordering by IbiPoint Data Rating, prices and a direct link included), but says nothing about rate limits, result caps, or empty-destination behavior, and the return detail is partly redundant with the existing output schema.

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 tight sentences, front-loaded with the core action and scope followed by usage. The closing 'with prices and a direct link' is mildly redundant given the output schema, but nothing else is wasted.

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?

For a read-only search tool with full schema coverage and an output schema, the description supplies purpose, scope, trigger context, and result ordering. Only the routing to sibling tools (details vs. checkout) is left unstated.

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 all four parameters (destination, type, currency, language) are already well documented, including the enum and the currency/language derivation. The description only restates the destination scope and adds no syntax or format detail beyond the schema.

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 ('Find') and resource ('eSIM plans') scoped to a destination, and adds concrete output semantics (best-value, sorted by IbiPoint Data Rating, with prices and a link). It is clearly distinct from the siblings get_plan_details and start_checkout, though it never names or contrasts them explicitly.

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?

Provides a clear trigger condition: 'Use when a user wants mobile data abroad.' However it gives no when-not guidance and never mentions the alternatives (get_plan_details for a specific plan, start_checkout to buy), so an agent must infer the boundary between searching, inspecting, and purchasing.

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