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

Annotations already establish this as read-only, idempotent, non-destructive, and closed-world. The description adds useful behavioral context beyond annotations: the plan links lead to an app page where the user completes payment, and the agent itself cannot perform payment or plan changes.

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?

The description is two front-loaded sentences, each carrying useful information: first what the plans contain, then how the upgrade link works and the agent's limitation. There is no filler or repetition of structured fields.

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, no output schema, and annotations already covering safety characteristics, the description supplies the missing return-value context: plan prices, allowances, inclusions, extra-video pricing, and links. It is complete enough for an agent to know what to expect and how to direct the user.

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 has zero parameters, so there is no parameter semantics to document in the description. The baseline for a parameterless tool is 4, and nothing in the description misrepresents the input shape.

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 clearly states the resource is HypeFox plans and enumerates the concrete contents: monthly and yearly prices, video/project allowances, plan inclusions, extra-video pricing, and per-plan app links. It distinguishes this informational lookup from plan-changing actions by explicitly noting that the agent cannot pay or change the plan itself.

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 clear context for use: retrieve plan details and provide the user with the in-app link where payment happens. It also explicitly excludes payment or plan changes by the agent. It stops short of naming a specific sibling tool for plan approval, but the boundary is clear from the description.

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