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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the read-only, externally-sourced nature is covered. The description adds a useful enumeration of what the response contains (data, validity, network, top-up, reviews, link), but since an output schema exists, this is supplementary rather than essential.

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 economical sentence that front-loads the resource and scope, with the field list compressed into a trailing enumeration. No filler.

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 annotations covering safety and an output schema covering return shape, the description needs only to identify the resource and scope, which it does. It lacks any routing hint toward search_esim_plans for id discovery, a minor gap given only three 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 both product_id and language are already documented in the schema, including the landing-page language/currency effect of language. The description only gestures at product_id, adding nothing beyond the structured fields; 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 (get) and resource (full details for one IbiPoint plan) scoped to a single product id, and enumerates the returned facets. This contrasts implicitly with the bulk-orientation of search_esim_plans, though the sibling is never named.

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 'by product id' implies the tool is used after obtaining an id, and the schema notes the id comes from search_esim_plans, but the description itself gives no explicit when/when-not guidance or naming of the alternative search flow.

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