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

Annotations already declare a safe, idempotent, closed-world read, and the description still adds substantial behavior: the pick rotates daily and is stable within a day for identical inputs, different inputs open different parts of the bench, and an impossible minutes constraint yields an honest 'shortest fit' fallback rather than fabrication. It also says what is returned verbatim (activity text, duration, what to grab), with no annotation contradiction.

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 tier mapping, then rotation and fallback behavior — a sensible ordering. The single long colon-chained opening sentence is dense, but each clause (tier semantics, determinism, fallback) carries distinct information that earns its place.

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?

There is no output schema, and the description compensates by naming the return fields (verbatim activity, duration, what to grab). For a two-optional-parameter read tool it also covers the non-obvious cases: same-input determinism, daily rotation, and the no-short-enough fallback, leaving nothing an agent needs in order 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 coverage is 100%, so baseline would be 3, but the description adds real meaning: it maps 'low'/'some'/'full' to empty-tank, small, and big tiers and explains that minutes acts as a hard cap on run length. It stops short of clarifying edge behavior for a fractional or boundary minutes value, which the schema's 1-120 range already covers.

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: it returns exactly one evening activity from a 27-item bench, constrained by energy and minutes. That is clearly distinguishable from get_lesson and search_lessons, though the near-sibling weekend_pick (an obvious alternative for a different day) is never named, so differentiation is implied by 'evening' rather than explicit.

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 rather than stated: the parent supplies the energy they have left and the minutes available, and 'Omit if any energy/length is fine' appears only in the schema. There is no explicit when-not guidance and no named alternative, so an agent must infer that weekend_pick or tonight_plan cover other planning horizons.

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