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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is partly covered. The description meaningfully adds that no reservation is made and that the check compares against existing blocked nights ('tileDisabled'), which is genuine behavioral context beyond the annotations. It does not note any rate limits or auth requirements.

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 short and front-loads the purpose before listing parameter formats and return values. The parameter-format sentence overlaps the schema, which is minor redundancy rather than waste. Structure is clean and scannable.

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 availability check with an output schema present, the description covers the operation, the date conventions, and the no-booking guarantee. Return fields are also enumerated even though the output schema already defines them, so nothing essential is missing.

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 three parameters including the accepted date formats and the 'check_out is not counted as a night' rule. The description restates this same content rather than adding new meaning. Baseline 3 is appropriate when the schema does the heavy lifting.

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 states a specific verb and resource: it checks whether a given listing ('e'lon') is free within a date range. The listing-level framing plus the listing_slug parameter helps distinguish it from the hotel-level sibling check_hotel_availability, though that sibling is never named. Clear purpose, but no explicit sibling differentiation.

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?

It clarifies that nothing is booked and that it only compares against existing occupied days, which implies a read-only pre-check use case. However, it never states when to prefer this over check_hotel_availability or search_rentals, nor any prerequisites beyond the parameter format. Usage is implied rather than stated.

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