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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description goes well beyond that by disclosing matching semantics, result ordering (local plans first, then regional/global), pagination via 'matches' and 'returned', unlimited-plan fair-use fields, voice-call fields, and localized URL behavior. This is rich, honest behavioral disclosure.

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?

The description is long but well-structured and front-loaded with the core purpose. Every paragraph adds needed operational detail, especially since there is no output schema. It is dense rather than bloated, though some sections could be tightened without losing value.

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 no output schema, the description carries the full burden of explaining return values, and it does so thoroughly: result fields, fair-use semantics, voice fields, localized purchase links, pagination, and search scope. An agent has enough information to call the tool correctly and interpret the response. The complexity is high and the description meets it.

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 each parameter is already documented in the schema. The description adds useful runtime context for 'limit' (raise it to see more results) and clarifies unlimited-plan behavior relevant to data filtering, but it does not materially expand the meaning of 'destination' or 'min_days' beyond what the schema already states. Baseline 3 is appropriate.

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 and resource: 'Search travel eSIM data plans by destination name.' It clearly states what the tool returns and how matching works, but it does not explicitly differentiate this from sibling tools get_plan or list_destinations. The purpose is unambiguous even though sibling differentiation is left to the names.

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 gives clear context on when to use the tool: search by destination name, search regions by their own names, and search 'global' for worldwide plans. It explains expected matching behavior and ordering, and gives practical guidance on pagination. It does not explicitly mention exclusions or when to prefer a sibling tool, but the usage context is strong.

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