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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the safety profile needs no restating. The description adds genuinely new context: pricing is quoted in NOK per year including 25% VAT, which an agent cannot infer from any structured field.

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 compact sentences with zero filler; the pricing/currency qualifier and the default-vs-category rule are both front-loaded and earn their space.

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 one-optional-parameter read tool with no output schema and strong annotations, the description supplies the essentials: what is returned, in what currency/units, and how the default differs from an explicit category. Minor gaps (e.g., ordering or list size limits) are not critical here.

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 coverage is 100% and the enum is fully documented in the schema, including the 'popular (default)' note, so the description's category sentence largely repeats structured data. Baseline 3 is appropriate.

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 ('List the domain extensions pekt sells') and additionally specifies the payload (first-year and renewal price). None of the siblings (check_domain, requirements, suggest_domains) perform a catalogue listing, so an agent can distinguish it immediately.

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?

Explicitly states the default behavior ('Default is the most popular ones') and the condition for deviating ('pass a category for others'). No exclusions or alternatives are named, but the branching rule is clear enough to act on.

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