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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: the data vintage (2022 census) and the exact metric set returned, which tells the agent what it is getting and how current it is.

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?

One compact sentence, front-loaded with the country scope, with no filler. It is dense but every clause carries information; the only minor cost is that density makes it read as a data blurb rather than an instruction.

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 single-parameter lookup with full annotation coverage and no output schema, the description supplies the needed scope: country, metrics, granularity and vintage. An agent can call it correctly without more, though a note on coverage limits (only largest cities, not all municipalities) would close the remaining gap.

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% and the single 'place' parameter already documents city/state examples and that empty means Germany. The description only restates the granularity (largest cities and 16 states), adding no syntax or format detail beyond the schema, so the baseline 3 applies.

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 names a specific dataset: average net cold rent per m², owner-occupation and vacancy rates, at census granularity (largest cities and the 16 states). This is far more specific than the tautological title and clearly separates it from sibling pricing tools like purchase_costs_de or mortgage_payment_de. It stops short of explicitly naming the sibling it is not, so a 5 is not warranted.

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?

There is no statement of when to use this tool versus alternatives (guide_de, compare_states_de, stats_marche, purchase_costs_de) and no exclusions or prerequisites. The metrics imply a use case, but nothing is written as guidance.

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