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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds useful calculation context by saying the fee is net and includes tiered, minimum, and closing fee components, though it does not describe the return shape or currency.

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?

The description is short and front-loads the core purpose and fee components. The English sentence largely duplicates the German sentence, so it is efficient but not maximally concise.

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 three-parameter calculator with full schema coverage and safety annotations, the description covers the computation scope and included fee components. Without an output schema, it could be more explicit about the returned fee format or currency, but it is otherwise sufficient.

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%, so the schema already documents all three parameters, including category enum, gross EUR sale_price, and default DE marketplace. The description adds net-vs-gross context for the fee but does not add parameter-specific constraints or syntax 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?

The description clearly identifies the resource as an Amazon referral fee for a given price, category, and marketplace, including tiered, minimum, and closing fee components. It is distinct from FBA fee/profit siblings by fee type, but it does not explicitly name or differentiate against those alternatives.

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: calculate the referral fee for a price in an Amazon category on DE/FR/IT/ES. The description does not state when to use this instead of estimate_fba_fee or calculate_amazon_fba_profit, nor does it give exclusions or prerequisites.

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