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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral detail beyond that — the answer is a designer rule of thumb and includes a link to sources — but says nothing about the assumptions behind the numbers (single row, overhang, minimum spacing) that would let an agent judge when the output is unreliable.

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?

Two tight sentences with the core question front-loaded and the outputs listed immediately, so an agent can scan it in one pass. The trailing sentence about the linked page is slightly meta but short enough to earn its place as return-value context.

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 four numeric inputs, 100% schema coverage, and no output schema, the description carries the remaining burden of describing the return values — which it does by naming the four computed quantities plus the source link. The main gap is unstated modeling assumptions, which matter for a rule-of-thumb calculator but are not strictly required to invoke it.

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%, with units and defaults documented for island, ceiling, counter, and pendant, so the baseline is 3. The description only loosely gestures at the parameters ('how high above the counter' hints at the ceiling/counter pair) and adds no interpretation beyond what the schema already states.

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 the exact resource (pendant lights over a kitchen island) and enumerates the four results it produces: count, spacing, end inset, and height above counter. That is far more specific than the sibling names (chandelier_size, ceiling_fan_size) need it to be, though it phrases the purpose as a question rather than a verb+resource statement.

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: it is clearly a planning/estimation tool for kitchen island pendants, and the fixture-specific framing separates it from the sizing siblings. There is no explicit 'use this when / use X instead' guidance, no mention of prerequisites, and no statement of limits (e.g., single-row assumptions).

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