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

Beyond the readOnly, idempotent, and non-destructive annotations, the description discloses substantial behavior: safety checks run first, crisis input gets a crisis answer, health questions get a not-medical-advice refusal, diagnostic questions get a can't-diagnose answer, no-fit cases return nearest lessons, and the tool never writes a new lesson. It also states the age band never changes matching and warns when the band is outside the toddler range, which is valuable context an agent could not infer from annotations alone.

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 description is front-loaded with the core purpose and then covers fallback and safety behavior in a logical order. It is somewhat long and repeats the point that age band does not change matching, but nearly every sentence carries useful information for invocation.

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 two-parameter lookup tool with no output schema, the description is complete: it explains what is returned, what happens when nothing matches, how safety cases are handled, and how the optional age band behaves. An agent has enough information to call the tool correctly and interpret the results.

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%, so the schema already documents both parameters, including the situation example and the age-band enum. The description reinforces that situation is a few of the parent's own words with no names or personal details and that age band is context only, but it adds little beyond the structured schema, so the baseline of 3 is appropriate.

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 states a specific verb and resource: it returns the one written lesson that matches the parent's described hard part, quoted word for word, and it lists the lesson components. This is clear enough for an agent to understand what the tool does, but it does not explicitly distinguish itself from the sibling search_lessons or tonight_plan tools.

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?

The description explains the matching behavior, the no-fit fallback, and the safety-first routing, which gives useful context for when the tool applies. However, it never names the sibling tools or states when an agent should choose get_lesson over search_lessons, tonight_plan, or the other activity tools, so selection guidance is only implied.

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