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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuine behavioral content beyond that: what the response covers (first-year vs renewal pricing, inclusions, free-trial and cancellation terms), which is useful for an agent deciding whether this call answers the user's question.

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 dense sentence that front-loads the returned data and then the modifiers, with no filler sentences. Slightly heavy prose 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?

An output schema exists, so return format need not be explained, and parameters are fully covered by the schema. The description supplies enough scope and content detail for an agent to invoke this confidently; only explicit usage routing 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?

Schema description coverage is 100%, so all four parameters (lang, service, currency, territory) are already fully documented in the schema. The description reinforces the service/territory semantics but adds no syntax, format, or constraint detail beyond what the schema supplies, making the 3 baseline correct.

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 ('Returns') and a precisely scoped resource: REP27 plans with first-year price, renewal price, inclusions, plus free-trial and cancellation terms. It also names the two service variants (GDPR Art. 27 vs GPSR Art. 16), which cleanly separates it from siblings like create_checkout and start_free_trial.

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 implied by the content description (use this to see pricing and terms), but there is no explicit when-to-use or when-not-to-use guidance, and no routing hint toward siblings such as start_free_trial or create_checkout. Adequate but leaves the agent to infer the selection context.

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