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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety is covered. The description adds real context beyond them: overnight sleep crossing midnight is attributed to the day, and it returns data only rather than rendering. It does not mention pagination or response size, but for a bounded one-day summary that is minor.

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?

Front-loaded with the core purpose, then the content list, then usage examples and the alternative. The enumeration is long but every item is a distinct output field, so it earns its space; slightly dense but no filler sentences.

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?

With an output schema present and annotations covering the safety profile, the description supplies everything else an agent needs: the aggregation rule for overnight sleep, example intents, and the routing to show_day. Nothing required to call it correctly is missing.

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 date, babyId, and timezone semantics (defaults, format, fallback behaviour) are fully documented in the schema. The description only implies date semantics via the midnight-crossing note, which does not extend beyond the schema. Baseline 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 and resource (summarise one calendar day for a baby) and enumerates exactly what the summary contains: sleep totals, counts, bottle ml, breastfeeding minutes, nappies, and a timeline. This clearly distinguishes it from the list_* and create_* siblings.

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?

Provides concrete triggering questions ('how did she sleep today?', 'how many feeds yesterday?') and explicitly routes to the alternative for visual output: 'to show the day visually, call show_day.' Both when-to-use and the alternative are stated.

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