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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful behavioral context — the result is day-by-day availability, and it maps to the GET /item/{item_id}/cal endpoints — but it says nothing about response shape, pagination, or date-range limits, so the added context is modest.

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 front-loaded sentences: scope first, then the use case, then the underlying API paths. Tight overall, though the raw endpoint reference is mildly redundant for an agent and slightly dilutes the clarity.

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, 4-parameter, non-required-parameter tool with no output schema, the description covers scope, granularity, and intent adequately. It leaves the shape of the returned calendar undocumented, which is a minor gap rather than a functional one.

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 description's mention of item_ids (one vs several) and category mirrors what the schema already documents for start_date, end_date, item_ids, and category_id. Baseline 3 applies because the schema does the heavy lifting and the description adds no new syntax or format 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 ('day-by-day available inventory over a date range') plus scope granularity (single item, several items, or a whole category). This distinguishes it cleanly from siblings like list_items or get_item, which return entity data rather than per-day availability.

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 a concrete use case — answering 'which days next month still have space?' — which tells the agent the right scenario. It does not name an explicit alternative or exclusion (e.g., when to prefer a booking search over the calendar), so it falls just short of a 5.

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