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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered. The description adds genuinely non-obvious behavior: the report has no paging and is capped at 200 rows, plus the mitigation. It stops short of describing row shape or truncation signaling, but this is real value beyond the annotations.

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 short sentences, zero filler, and the most decision-relevant facts (scope, row cap, sibling alternative) are front-loaded. Every sentence earns its place.

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?

Given a simple 4-parameter read with no output schema, the description covers scope, cardinality limits, mitigation, sibling routing, and the underlying endpoint. Nothing an agent needs to invoke it correctly is missing.

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 baseline is 3, but the description adds purpose to the two optional filters beyond the schema's terse 'Only this location'/'Only this leave category' – they are the levers for staying under the 200-row cap. That extra semantics justifies a 4.

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+scope: leave balances of all employees as at a date, per leave category. It also distinguishes itself from the single-employee sibling keypay_get_leave_balances, so an agent can route correctly without opening either 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?

Explicitly names the alternative ('For one employee use keypay_get_leave_balances') and gives the condition that selects it. It also tells the agent when to narrow with location_id or leave_category_id, i.e. when the 200-row cap would bite.

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