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

Goes well beyond the destructiveHint=true annotation by disclosing partial-update semantics ('what is not given stays as it was'), the null-minutes reset to a whole working day, the re-approval side effect, the privacy boundary on notes, and the post-write validation rule (max 366 days, end on/after start). These are exactly the consequences an agent needs before calling a destructive mutation.

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?

Two sentences, front-loaded with the change semantics before the permission and validation clauses. The nested parentheticals make it dense and slightly hard to scan, but every clause carries distinct information.

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?

Covers permissions, partial-update behavior, approval side effects and validation for a destructive mutation with no output schema. The only gap is that it never says what the response contains (the updated record vs just an acknowledgement), which matters modestly when the caller needs to confirm the new state.

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 baseline is 3, but the description adds real meaning the schema lacks: the partial-update contract for every optional field and the fact that null minutes restores a full working day. It does not add anything for timeOffId beyond what the schema already states.

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 (changes) plus the exact mutable fields of a named resource (kind, days, minutes per day, note of a time off). It is clearly a mutation of an existing record, which implicitly separates it from add_time_off/remove_time_off, though no sibling is named.

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 applicability conditions: a person edits their own time off, and on Pro a project owner can edit their editors' time off (note excluded). It also specifies that changing kind/days/minutes on an approved or rejected entry triggers re-approval. It stops short of explicitly naming alternatives like approve_time_off or remove_time_off, so no explicit when-not guidance.

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