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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new context: the returned data is fictional and there is no account connection, which is exactly the kind of caveat an agent needs to avoid presenting samples as real eSIMs. It stops short of describing return shape, but an output schema exists.

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?

Three short sentences, no filler, and the most important qualifier (fictional data, no account connection) lands early. The lead sentence is the weakest element because it front-loads a vague reference to the website rather than the tool's function, but the total length is well within budget.

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 rich annotations, the remaining descriptive burden is small: confirm the data is fake and isolated from the account, which it does. Nothing an agent needs in order to call this correctly appears to be missing, though a hint about what the samples illustrate would round it out.

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, so there is nothing for the description to disambiguate. Schema coverage is 100% and the parameter set is empty, which is the baseline-4 case by rule.

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 states the resource plainly: it returns 'explicitly fictional example profiles', which tells an agent this is a sample/demo listing rather than real user data. The opening sentence ('Matches the free website sample preview') is a slightly opaque framing, but the second sentence disambiguates it from the real-data siblings. A reader can distinguish it from list_available_plans or recommend_plan without opening the schema.

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 implicitly defines the use case (demo/preview content, not real balances), and the 'never your real eSIMs' clause rules out the misconception that this reads account data. However, it never explicitly says when to call this versus a real plan-listing tool, nor names an alternative. Usage is inferable but not guided.

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