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

Annotations already indicate readOnlyHint=true and openWorldHint=true, so description does not need to restate safety. It adds value by mentioning real catalog prices, instant delivery, and types of plans (unlimited, combo). No contradictions.

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 are efficient and front-loaded with the main action. The second sentence lists use cases without excessive detail. Could be slightly more structured, but overall concise and clear.

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?

No output schema, so description explains return content: data packages by GB, validity days, unlimited/data+calls+texts options, and pricing in USD. This gives a solid understanding of what the tool returns. Annotations cover read-only and open-world aspects, making it fairly 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?

Input schema covers 100% of parameters with descriptions (destination, days). The description reinforces that destination is a country/region in English and that days is optional for filtering. It provides usage context but does not add significant new semantics 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?

Description clearly states the tool finds prepaid travel eSIM data plans for a destination, listing key attributes (prices, data packages, validity, options). It distinguishes from siblings (e.g., car rentals, tours) by focusing exclusively on eSIM search.

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?

Explicitly states when to use: for buying eSIM/SIM, getting mobile data abroad, avoiding roaming charges. Examples like 'eSIM for Italy' clarify typical queries. Does not explicitly state when not to use, but sibling tools cover different domains, so confusion is unlikely.

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