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

Annotations already flag destructiveHint=true and readOnlyHint=false, so the safety profile is covered; the description goes further by disclosing real side effects: capacity is lowered, the person is notified, the note is read by both the person and owners, and a Pro/team-calendar requirement gates the call. It falls short of stating reversibility (whether a rejection can be undone) or what happens on error, which would be needed for 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?

Three sentences, front-loaded with the verb and effect, and each subsequent sentence carries distinct information (side effect, Pro prerequisite, confirm requirement). The opening clause is grammatically tangled ('Rejects a time off an editor of a project the user owns asked for'), costing a bit of readability.

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 three-parameter mutation with no output schema, the description covers the capacity effect, notification behavior, licensing prerequisite, and the confirm-gated preview, which is what an agent needs to call it safely. Missing only the reversibility/undo path and how conflicts with already-processed requests are surfaced.

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 all three parameters including the 300-character note limit and the confirm-preview semantics are already documented in the schema. The description only restates the notify/read-by behavior and the confirm requirement rather than adding format or edge-case detail beyond it, so the baseline of 3 applies.

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 (rejects) and resource (time off) and narrows scope to requests from an editor of a project the user owns, or already-approved requests. An agent can tell it is a state-changing decision on an existing time off request. It does not name how it differs from adjacent siblings like remove_time_off, update_time_off, or approve_time_off, so the differentiation is inferred rather than explicit.

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?

Conveys when the tool applies (pending or previously approved requests) and a critical invocation rule: confirm: true is required or you get a preview. However, it never says when to prefer reject_time_off over remove_time_off or update_time_off, nor does it state what preconditions (e.g. request must still be pending) block the call.

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