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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is context-adding; the description discloses that results are permission-scoped by role (own / reports' / everyone's) and that listing is ordered 'earliest start first'. It doesn't spell out pagination behavior beyond the schema's limit field, but the role-visibility rule is substantive value.

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?

Front-loaded with the core behavior, then the parameter-driven variants, then example questions. Every sentence carries information, though the prose is dense and slightly run-on.

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 and annotations covering safety, the description need not explain return values; it fully covers scope, ordering, per-role visibility, and mode-switching, leaving nothing an agent needs before calling it.

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; the description goes further by explaining the temporal overlap semantics of from/to ('leave that overlaps those days') and the meaning of the status combination, adding interpretation beyond the field-level text.

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 ('Lists time off and leave requests') and also covers the single-record read mode ('or reads one by its id'). No sibling tool covers PTO data, so the agent can place it immediately among the invoice/project/task listers.

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?

Gives clear conditional guidance: 'With from and to it lists leave that overlaps those days... with status approved that shows who is out', and illustrates with example questions. It doesn't name an alternative tool, but no sibling overlaps, so exclusions are unnecessary.

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