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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety profile is covered; the description adds the legal basis and thresholds. However, with no output schema, the description says nothing about what the calculation returns (a payable amount? eligibility boolean?), which is a real gap for a calculator tool.

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 sentences, front-loaded with the regulatory basis and eligibility rules; almost no waste. The parenthetical is dense but functional, and the trailing English tagline adds little.

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?

Eligibility conditions are well covered for a five-parameter legal calculator, but with no output schema the description should describe the returned result (amount, currency, partial entitlement) and it does not. That omission leaves the agent guessing about the response.

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 baseline is 3, but the description adds regulatory meaning the schema lacks: the 250 km distance floor and the 120-minute delay threshold give the agent context for what values of distance_km and departure_delay_min actually trigger compensation.

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 (Prüft/checks the compensation) and resource (Fernbus under VO (EU) 181/2011), and names the exact trigger conditions. It is clearly distinguishable from calculate_flight_compensation, calculate_train_compensation and calculate_ship_compensation without opening any schema.

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?

The description spells out the eligibility context (route from 250 km, cancellation, or more than 120 minutes departure delay), which tells the agent when this tool applies. It does not explicitly name the sibling tools or state when NOT to use it, so it stops short of a 5.

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