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

Annotations only declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, which says little about side effects. The description supplies the substantive semantics: a skipped day does not count against the goal and does not break the streak, plus a hard lookback limit of 7 days. That is real behavioral context the annotations do not carry.

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 tight sentences: what it does, the key side-effect guarantee, the scope limit, and the alternative. The primary action and its most surprising property (streak-safe) are front-loaded, and nothing is filler.

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?

An output schema exists, so return values need not be explained. Given a single-required-param mutation, the description covers trigger, side effects, backdating limit, exclusions, and the sibling alternative — everything needed to call it correctly.

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 description coverage is 100%, including the date format, timezone, default-to-today behavior, and reason phrasing, so the schema already carries the parameter burden. The description adds only the framing that the topic must have a goal and that the reason is the person's own words. Baseline 3 is appropriate.

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 with scope: 'Takes one day off one topic with a goal.' It also names what it is not (not for tasks) and which sibling covers the broader case (pause_days), so an agent can separate it from unskip and pause_days without opening a 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?

Explicit trigger condition ('when the person says so'), an explicit exclusion ('not for tasks (move their due date instead)'), and a named alternative ('For time off across everything, use pause_days'). Both the when and the when-not are stated rather than implied.

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