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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the safety profile is covered. The description adds genuine value beyond that by disclosing the return contents: cheapest eligible plan, prices and limits of all plans, and a register link, which tells the agent what a call yields.

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 action and its inputs, with no filler. Slightly dense with multiple clauses, but every clause carries information.

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 simple read-only, single-required-parameter tool with no output schema, the description covers the inputs, the selection logic (cheapest), and the shape of the response. Nothing critical is missing, though noting the pre-checkout placement 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?

Schema description coverage is 100%, so the schema already documents locale, domains, and pageview limits/units thoroughly. The description only restates that monthly_pageviews is user-stated traffic; it adds no syntax or edge-case guidance beyond the schema, 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?

States a specific verb and resource ('Recommends the cheapest CookiePilot plan') with the exact inputs that drive the recommendation and what is returned. Clearly distinguishable from siblings like create_account or start_checkout, which act on a chosen plan rather than selecting one.

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: the word 'Recommends' plus the pricing/register-link return hints this is a pre-purchase step before create_account or start_checkout, but the description never says when to use it or when not to. No alternatives are named.

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