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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description still earns credit by disclosing the return contents and explicitly ruling out side effects ('does not book or hold the dates'). It implies freshness ('live') but doesn't warn that prices/availability can change between calls or note any rate limits.

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: the valuable one first (what comes back), then the short scope negation. The parenthetical breakdown is dense with information and nothing is repeated from the schema or annotations.

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 no output schema, the description carries the burden of describing return values and does so concretely (cost components, total, per-rate cancellation terms, booking link). Combined with fully documented parameters and read-only annotations, an agent has everything needed to call it and interpret the result.

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% with per-parameter descriptions (date formats, pet limits, defaults, enum languages), so the schema does the heavy lifting. The description only implicitly touches parameters by naming 'nights, pet fee, taxes', which hints at occupants/pets mattering for pricing but adds no syntax or constraint detail.

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+resource — 'Exact live quote for one apartment' — and enumerates the payload (price breakdown by component, total, per-rate cancellation policy, pre-filled booking link). This distinguishes it cleanly from get_apartment_details (static info), get_policies (rules), and search_availability (discovery rather than a priced quote).

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?

'Exact live quote for one apartment' plus 'Does not book or hold the dates' establishes context: it's the priced step for a single already-chosen apartment, not a booking action. It stops short of explicitly routing to siblings (e.g., use search_availability first to find a free apartment), so no alternative is named.

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