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 covered. The description adds a genuine scope boundary (top-up eligibility is reported elsewhere) that annotations do not convey, but says nothing about auth, rate limits, or lookup failure behavior for an unknown destination.

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?

Front-loaded with the return payload, followed by input format and usage routing. The long enumeration of returned fields is dense but each item is informative; little waste, though it could be trimmed given an output schema exists.

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?

Covers input formats, default currency behavior, relationship to sibling tools, and an explicit scope exclusion. With annotations carrying the safety profile and an output schema describing the payload shape, nothing needed to call this correctly is missing.

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 100%, so both parameters are fully documented in the input schema. The description restates the accepted destination formats and currency default, which is mildly reinforcing but largely duplicative; baseline 3 applies.

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+resource (details for one destination) and enumerates exactly what is returned: name/codes, region, plan counts, price extremes, bundle extremes, storefront page. The sibling tool it relates to (list-plans) is named, so an agent can distinguish the two without opening schemas.

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?

Explicit sequencing guidance ('use this to describe a destination before pulling its full plan ladder with list-plans') plus an explicit exclusion ('Whether a plan can be topped up ... is reported by list-plans, not here'). Both when-to-use and when-not-to-use are stated.

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