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

Annotations already cover readOnly, idempotent, non-destructive and closed-world, so the safety burden is light. The description adds genuinely new behavioral context: the numbers include only confirmed reservations and are stated to match the panel's Statystyki page, which tells the agent what the figures represent and that they are UI-congruent. It could still note whether results are cached or rate limited.

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 dense sentences, front-loaded with the metric and granularity, followed by the required-parameter rationale. Every clause carries information; no filler.

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?

With an output schema present, return values need no explanation, and the description covers granularity, scope, filtering, and the mandatory-parameter rationale. Only minor details (time basis for 'monthly', any auth context) are absent, which is acceptable for a read-only stat tool.

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 a baseline of 3 applies, but the description goes beyond the schema by explaining why apartment_id is mandatory — occupancy/revenue from apartments with differing nightly rates can't be meaningfully aggregated. That rationale is not present in the schema and materially helps the caller.

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 verb+resource ('Monthly occupancy and revenue'), the granularity ('monthly'), the scope ('one apartment'), and the filter ('confirmed reservations only'). It is unambiguous what is returned, though it never explicitly contrasts itself with siblings like get_availability or get_pricing.

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 rather than stated: it makes clear apartment_id is required and warns that rates can't be summed across apartments, steering the agent to call it per-apartment. However, there is no explicit 'use this instead of X' routing against the other stats-adjacent siblings such as get_pricing or get_availability.

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