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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description goes further by disclosing the exact computation rules (area = length × width, span brackets, shorter-side − 36 in, mount thresholds). It also names what the response will contain, which matters since no output schema exists. It does not state how defaults are applied when parameters are omitted.

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 outcome before the supporting formulas, and every clause (brackets, clearance rule, mount thresholds) carries operative information. It is dense and semicolon-chained, which slightly hurts scannability, but there is no 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?

With no output schema, the description must convey return values, and it does (span, max span, mount type). Inputs are fully documented in the schema and their roles are explained here. Minor gap: it doesn't say what happens for edge cases such as non-rectangular rooms or omitted parameters.

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 the baseline would be 3, but the description adds real semantics: width and length combine into area for span lookup, and ceiling_height_ft maps directly to the mount decision thresholds. The wall-clearance formula also clarifies that the shorter side drives the maximum-span result.

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?

Opens with a specific verb+resource framing ('What size ceiling fan you need for a room') and enumerates the three outputs: suggested blade span, largest span with 18 in wall clearance, and mount type. An agent can distinguish this from siblings like calc_ac_btu or calc_attic_ventilation without opening the schema.

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 by the domain framing (size a fan for a given room), but there is no explicit when-to-use/when-not-to-use guidance and no named alternative among the many sibling calculators. Nothing is misleading, but the agent must infer the triggering context.

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