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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed world, so the safety profile is covered. The description adds genuinely new behavioral context beyond them: the data is public and requires no sign-in, which affects how the agent may call it. It does not mention caching, freshness, or currency-conversion caveats, so it stops short of a 5.

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?

Two sentences, zero waste: the first front-loads the payload (plans, prices, purpose, offers), the second front-loads the access condition. Nothing is repeated from the schema or annotations.

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 an output schema present, the description has no obligation to explain return values, and with no parameters there is no input ambiguity to resolve. Combined with annotations covering the safety profile and the description covering access and content scope, an agent has everything needed to call this correctly.

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; the baseline for a parameterless tool applies. The description correctly signals that this is a single-shot, no-input lookup.

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 resource (plans and prices) and enumerates the exact plans returned (Creator Audit, Monitoring, Studio, Agency), plus the extras included (what each plan is for, current offers). An agent can distinguish this from info siblings like about_whichpost, get_faq, or how_it_works without opening any 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?

"Public information; needs no sign-in" tells the agent no auth is required, but there is no explicit when-to-use or when-not-to-use guidance relative to the other informational siblings. Usage is only implied (call it when pricing is needed).

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