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

Annotations already cover the safety profile (readOnly, idempotent, closed-world, non-destructive), so the description's job is to add context. It does: it discloses the actual compliance thresholds and, importantly, that 'Every sliding window is checked' rather than just daily totals — a behavior an agent could not infer from annotations or schema. It stops short of describing what a failing result looks like.

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?

One front-loaded sentence with the substance first (what is checked, against which rule) and the optional towing extension last. The parenthetical threshold list is dense but each clause carries real information; nothing is padding.

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 read-only validator with no output schema, the description should indicate what comes back (violations, per-window results, pass/fail) and how the from/to parameters interact with the work array. Those gaps are real, but the core rule content is fully specified, which is the harder part.

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 baseline is 3. The description adds regulatory grounding for the towing boolean (12-hour limit under 46 U.S.C. 8104(h)) and explains the semantics of 'work' periods through the ruleset, but says nothing about the from/to window bounds or the work-item kind enum.

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?

Specific verb and resource: 'Check work periods against STCW hours of rest' with the exact regulatory thresholds enumerated. It clearly separates itself from a general hours-of-service checker by naming STCW and 46 CFR 15.1111, though it never names a sibling tool as the alternative.

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?

Usage is implied by the enumerated rules rather than stated: an agent can infer this is the STCW/mariner rest check. There is no explicit when-to-use, when-not-to-use, or guidance on choosing this over hos_check or dq_file_check.

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