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

No annotations are provided, so the description carries the full behavioral burden. It does disclose a genuinely useful domain model (a care day costs exactly one vacation day; a joint family holiday costs two and covers one; roughly 60 working days vs 25-30 days of account), which is real context beyond the schema. It stops short of describing permissions, error conditions, or the shape of the result.

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?

Three sentences, front-loaded with the core computation before the supporting arithmetic. Each sentence contributes: purpose, cost model, and the target user's question. Slightly dense but no wasted 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 six parameters, no output schema, and no annotations, the description should do more. It hints at the return ('which weeks stay open') but never explains the result structure, units, or how coverage is reported, leaving an agent guessing about the response format.

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 six parameters, including the jointDays costing rule. The description restates the same arithmetic model rather than adding syntax, defaults, or edge-case meaning beyond what the schema provides, so the baseline of 3 applies.

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 gives a specific verb+resource: it computes how much of a region's school holidays two vacation accounts cover, and which weeks remain uncovered. That is concrete enough for an agent to know what comes back. It does not name or differentiate itself from siblings like plan_vacation or public_and_school_holidays, so it falls short of a 5.

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 by the framing question 'can we cover the school holidays' for parents, which signals the planning scenario. However, there is no explicit when-to-use versus when-not, and no routing to alternatives such as best_bridge_days or plan_vacation. Adequate but with clear gaps.

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