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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is fully covered, and an output schema exists to explain returns. The description adds only the content scope and the note that answers are 'in the shop's own words' (authoritative, verbatim), which is modest added value rather than rich 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?

It is two sentences, front-loaded with the subject matter and ending on the routing rule. The topic list is dense but each item earns its place by signalling coverage. Minor cost: the enumeration reads as a run-on rather than a structured list.

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 parameters, a full output schema, and annotations covering safety, the description only needs to convey scope and when to call it - both are present and unambiguous. Nothing an agent needs to invoke 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?

The tool takes zero parameters and the schema is trivially covered, so there is nothing for the description to disambiguate. Baseline of 4 applies for a no-parameter tool.

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 enumerates the concrete content the tool returns (delivery/installation, device requirements, payment methods, refund policy, hotspot, support/company details), which makes the resource unmistakable. It also distinguishes itself from the plan-oriented siblings with 'not about one specific plan.' The only weakness is that the retrieval verb is implied rather than stated directly.

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?

It gives an explicit routing rule: use for any 'how / when / what if' question, plus the exclusion that bounds it away from plan-specific queries. That is enough to separate it from get_plan_details and search_esim_plans without opening any schema.

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