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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds useful behavioral context (the per-category breakdown and the as-at-date default of today), but says nothing about pagination, empty results, or how the balance unit is expressed.

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?

A single compact sentence front-loads the resource and the return shape, with the optional date qualifier attached. The trailing URL is redundant boilerplate but does not bloat or bury the key content.

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 no output schema, the description carries the return-value burden and does so adequately by naming the per-category accrued amount and unit. For a simple read-only lookup with fully-documented parameters, nothing essential is missing, though it could note what happens when no balance exists.

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 all three parameters are already documented in the schema, including the yyyy-mm-dd format and the 'default today' behavior. The description only restates the optional date, so it adds no meaning beyond the schema; 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?

States a specific verb+resource: retrieving an employee's leave balances broken down per leave category, optionally as at a date. It also discloses the return content (accrued amount and unit), which distinguishes it from list-type siblings, though it never names the closest-looking alternative keypay_report_leave_balances.

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?

The description gives no when-to-use guidance, no prerequisites (e.g., that business_id and employee_id are required), and does not distinguish this tool from the similarly-named sibling keypay_report_leave_balances. Usage is only inferable from the name and the 'optionally as at a date' wording.

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