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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds pagination (25 per page) and the underlying GET endpoint, which is useful operational context, but says nothing about permissions needed to read another employee's entitlements or how expiry/carry-over values are computed.

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?

Front-loaded with the resource and returned fields, compact at three sentences. The trailing 'GET /vacation_entitlements' is marginal value for an agent and page size is duplicated from the schema, but nothing is padded or confusing.

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?

No output schema exists, so the description helpfully enumerates the returned fields (planned days, spent days, expiry, carry-over) and page size, which compensates for that gap. With 100% schema coverage on the four parameters and annotations covering safety, the only remaining gap is permission/scope behavior for reading another user's data.

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 page, user_id, start_date and end_date are already fully documented in the schema. The description only adds 'for the given period', which vaguely frames the date filters without adding syntax or semantics beyond the schema's yyyy-mm-dd pattern definitions. 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?

Names the resource (vacation entitlements) and enumerates the concrete fields returned (planned days, spent days, expiry, carry-over) scoped to a period. The verb 'list' is only implied from the name/title, but the 'how many vacation days does X have left' framing makes the operation unambiguous and separates it from siblings like list_target_hours or list_absences.

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?

Provides an explicit usage context: answering 'how many vacation days does X have left'. This makes the intended scenario concrete. However, it names no alternatives or exclusions (e.g., when to use list_absences instead for actual absences), so the agent must infer boundaries.

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