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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered without description help. The description adds a real behavioral guarantee beyond that: the data comes from the same source the pricing page renders, telling the agent the answer is authoritative and consistent with the public site. It stops short of describing freshness, caching, or response shape.

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 sentence that front-loads the resource (plans, prices, limits) and closes with the source-of-truth guarantee. Every clause earns its place with 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?

For a zero-required-parameter read tool with full schema coverage and annotations, the description covers both what is returned and where the data comes from. The absence of an output schema means the agent still doesn't know the response structure or currency formatting, but nothing essential to invoking it 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?

With only one optional parameter and 100% schema description coverage, the schema carries the full explanation, including the surprising fact that pricing is identical in every country and the code is merely echoed back. The description adds nothing about the country parameter, so the 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?

The description names a specific resource (subscription plans, prices, per-plan limits) and a clear read action, so an agent knows exactly what it returns. It does not explicitly contrast itself with siblings like get_country_info or get_page, though the naming is distinct enough to avoid confusion.

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?

Usage is only implied: an agent can infer this is the tool for pricing questions because it returns plans and prices. There is no explicit when-to-use statement, no exclusion of alternatives, and no mention of prerequisites or how it relates to get_country_info.

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