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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the read-only safety profile is known. The description adds behavioral context beyond annotations: it returns live plans (not cached), filters to those covering every requested destination, considers pricing factors, and provides a checkout URL for purchase. This adds meaningful behavior without contradicting the annotations.

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?

Two sentences deliver all essential information: the core action and the follow-up. The main verb and resource are front-loaded, and every phrase adds value. No filler or redundant repetition of schema data.

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 enumerate return fields. It sufficiently covers the tool's purpose, constraints ('up to five', 'cover every requested country'), the key input dimensions, and the practical next step ('Use the returned checkout URL to buy'). This is complete for a tool of moderate complexity with no siblings.

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 five parameters are documented. The description reinforces the relevance of trip length, data need, currency, and locale, but does not add new details beyond what the schema already provides. This matches the baseline expectation for high schema coverage.

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 opens with a specific verb ('Finds') and resource ('live eSIM plans'), quantifies the result ('up to five'), and defines scope ('cover every requested country or region'). It clearly distinguishes this from a generic plan search by emphasizing the live and multi-destination coverage aspects.

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 conveys when to use the tool: when you need eSIM plans for specific destinations and a trip duration. The phrase 'priced for the trip length, data need, currency, and locale' implies criteria for selection, and the final sentence gives the next step. No exclusions or alternatives are stated, but sibling tools are absent, so the lack of contrast is acceptable.

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