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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: accrual pauses at the cap and resumes after time is used, which affects how projections should be interpreted. It stops short of stating other modeling assumptions (e.g. how starting_balance_hours interacts with hours_used_this_year), keeping it below a 5.

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 capability statement is front-loaded in the first sentence, followed by use cases and then the alternative-tool routing, so the most important content comes first. The opening sentence is long and packs three output dimensions plus the balance, but nothing is truly redundant.

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 an output schema present, the description need not explain return values, and it covers purpose, use cases, cap behavior and sibling routing. Only the interaction between starting balance, hours used and period count is left implicit, a minor gap for a 9-parameter pure-calculation tool.

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 coverage is 100%, so every parameter is already documented in the schema, establishing a baseline of 3. The description only reiterates the optional cap and hours-already-used inputs without adding format, interaction or defaulting guidance beyond what the schema says.

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 names a specific computation ('how paid time off accrues') and enumerates exactly what is produced: hours per pay period, per month, per hour worked, plus balance after each period. It explicitly contrasts with the pay-related siblings, so an agent can distinguish it from hourly_to_salary or overtime_pay without opening the schema.

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 gives two concrete use cases ('design or explain a PTO policy', 'project an employee's balance by year end') and an explicit exclusion routing pay questions to hourly_to_salary or salary_increase. When-to-use, when-not-to-use, and the alternatives are all stated.

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