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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered elsewhere. The description adds no behavioral context of its own: it says nothing about error behavior for unknown skus, response latency, or what the returned plan object contains. With no output schema, that is a missed opportunity rather than an error.

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?

A single front-loaded sentence with zero filler: verb, resource, key, and provenance. Nothing repeats the title or annotations.

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 detail lookup the safety and identity story is complete, but with no output schema and no description of the returned plan fields, an agent cannot anticipate what a successful call yields or how to handle an invalid sku. Adequate, not 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?

Schema coverage is 50% (locale is richly documented in the schema, sku is not). The description does compensate partly for the undocumented sku by telling the agent where the value originates (search_plans/recommend_plan), which is genuinely useful. It adds nothing about locale, which the schema already handles.

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?

Names a specific verb (Get) and resource (one eSIM plan) plus the identifying key (sku), and ties the tool to its place in the workflow by noting the sku comes from search_plans or recommend_plan. It never explicitly contrasts itself with siblings like get_destination_info, but the resource is unambiguous.

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 phrase 'as returned by search_plans or recommend_plan' establishes the precondition for calling it: you already have a sku from a prior search or recommendation. There is no explicit when-not guidance, but the usage context is clear enough for an agent to route correctly.

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