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

Annotations cover the safety profile (idempotent, non-destructive, non-read-only), and the description adds genuine domain behavior: a skipped day does not count against the goal and does not break the streak, and only up to 7 days back. That is real context beyond structured fields. It could say more about re-skipping or what the streak/goal state looks like afterward, but the output schema covers return values.

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 tightly packed sentences, front-loaded with the core purpose, then the behavioral rule, then the boundary conditions and the sibling pointer. No filler; every clause carries 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?

For a 3-param mutation with full schema coverage, annotations, and an output schema, nothing an agent needs to select and call it correctly is missing: purpose, trigger, exceptions, window, and sibling routing are all stated.

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 schema already documents day, reason, and topicId including formats and the today-default. The description adds no syntax or format detail beyond that, 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+resource+scope ('takes one day off one topic with a goal') and explicitly carves out what it is not: not for tasks, not organization-wide. An agent can distinguish it from pause_days and unskip without reading either 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 the triggering condition with a natural-language example ('skip stretching today, my back hurts'), names the exclusion (tasks -> move their due date), and routes to the alternative (pause_days for time off across everything). When/when-not/alternatives are all present.

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