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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable behavioral context: it explains the derivation of monthly rent (annual/12) and per-sqm rent (annual/area), clarifies that rentPerSqm refers to the actual apartment's area rather than the reference apartment's area, and discloses the attribution field requirement. This goes beyond what annotations provide.

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 a single, information-dense paragraph. It front-loads the core purpose and then details outputs and caveats. It's slightly long but every sentence adds value: the derivation formulas, the reference apartment distinction, and the attribution requirement are all necessary. No wasted words.

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 read-only calculation tool with 100% schema coverage and no output schema, the description is quite complete. It explains the output fields, their derivations, the reference apartment caveat, and the attribution requirement. The only minor gap is that it doesn't explicitly state what happens if correctionPoints is omitted (though the schema says default 0), and it doesn't describe error conditions. But overall, an agent has enough to call it correctly.

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 schema already documents all four parameters. The description adds context about how the parameters relate (normhyra is per m²/year, area is the actual apartment's area, correctionPoints are optional) but doesn't add syntax or format details beyond the schema. 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?

The description clearly states the tool's purpose: converting a normhyra (kr/m²/år) into actual annual rent in kronor for a given apartment type, area, and optional correction points. It specifies the exact outputs (rent78, rent91, rent12, monthly equivalents, and per-sqm values) and distinguishes itself from related tools by naming the reference apartment (3 rok 77 m²) and the attribution requirement.

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 explains when to use this tool: when you need to convert a normhyra to actual rent for a specific apartment. It doesn't explicitly name alternatives or exclusions, but the sibling context (calculate_normhyra, calculate_rent_roll, export_rent_roll_pdf, list_apartment_types) makes the use case clear. The description also notes that the calling model doesn't need to do the conversion itself, which is a useful usage hint.

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