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

Annotations already declare non-readonly, non-destructive, idempotent, and closed-world behavior; the description still adds real value with the OWNER/ADMIN authorization requirement, active-member eligibility rule, and PRO+ feature gate. It redundantly restates idempotency, which the annotation already conveys, keeping it out of 5 territory.

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?

Four short sentences with the core action front-loaded and constraints trailing; no filler, no restated title, and every sentence carries a distinct rule.

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?

For a one-parameter mutation with no output schema and rich annotations, the description supplies purpose, permissions, idempotency, eligibility, and feature gating. Nothing an agent needs in order 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 the single userId parameter is already documented as the 'Org member ID to designate as approver.' The description adds the constraint that the referenced user must be an active org member, which is a genuine eligibility rule beyond the schema 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 and resource ('Add a user to the designated timesheet approver list'), which unambiguously distinguishes it from list_timesheet_approvers and the approve/reject_timesheet_* siblings. An agent can identify the operation without opening any 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?

Gives concrete preconditions — requires OWNER or ADMIN, target must be an active org member, and the timeTracking (PRO+) feature must be enabled — so the agent knows when the call will succeed. However, it names no alternative tool (e.g., list_timesheet_approvers or update_member_role) and states no explicit when-not condition, so it stops short of a 5.

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