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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety burden is light. The description still adds real behavioral context beyond them: output is deterministic per date ('the same date always gives the same plan'), there is no per-family memory, and the site's 'Another one' swap is not an input — which preempts an agent from hunting for a variation/seed parameter.

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?

The content is front-loaded, leading with what the plan is and following with the components, then the determinism and no-memory caveats. The enumerative first sentence is long and dense, but each clause (activity duration, what to grab, lesson quoted in full with puzzle line) carries genuine information rather than 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?

There is no output schema, so the description must carry the return-value burden, and it does — listing every section of the plan and noting the lesson is quoted in full with its puzzle line. Combined with the stated determinism and absence of per-family state, an agent has everything needed to call this correctly and to interpret the response.

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% and the single date parameter is fully documented in the schema, including the local-vs-UTC nuance, so the description need not repeat it. The line 'the plan is fixed by the date' reinforces the parameter's role but adds no format or syntax detail 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?

The description names a concrete resource (the full evening plan for a given date) and enumerates its parts — dinner, phone line, activity block, bath, close, parent's hour — so an agent knows exactly what comes back. It does not explicitly name the sibling tools (get_lesson, pick_activity) or state that this is the whole-evening counterpart to their fragments, leaving that distinction implicit.

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: because the tool returns the entire evening and the lesson 'rides inside the block', an agent can infer this is the pick when the whole plan is wanted and get_lesson/pick_activity are for single pieces. There is no explicit when-to-use, when-not-to-use, or named alternative anywhere in the text.

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