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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety bar is met. The description adds real value beyond that: it discloses the currency conversion source (ECB rate) and the constraint that GPSR is always eu territory, which an agent would otherwise not know.

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 returned content and packs scope constraints into the tail with no filler. Every clause earns its place.

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?

Output schema exists so return shape needn't be explained, annotations cover the safety profile, and all four parameters are fully documented in the schema. The description supplies the remaining business context (what the prices mean, trial/cancellation terms) without gaps.

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 baseline is 3. The description restates territory options and the GDPR/GPSR distinction already documented in the enum descriptions, adding little new parameter meaning beyond the schema.

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 ('Returns REP27 plans') plus exactly what data comes back: first-year price, renewal price, inclusions, trial and cancellation terms. It is clearly distinguishable from siblings like check_obligations or start_free_trial, though it never names an alternative explicitly.

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 pricing lookup tool versus about_rep27 (general info) or create_checkout (purchase). There is no explicit when-to-use, when-not-to-use, or named alternative, which matters given five adjacent tools in a purchase flow.

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