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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds that CAC is treated as fully-loaded and that results are computed on two bases, which is modest value, but it discloses nothing about output shape, rounding, or edge cases like zero gross margin.

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 core sentence is front-loaded, precise, and wastes no words. The trailing URL is a self-promotional line that does not help invocation, costing it a perfect score.

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?

A small three-parameter calculator with full schema coverage and no output schema, so the description need not explain returns. Still, it never states what the tool produces (months per basis) or how the two bases are reported, leaving an agent to infer the result format.

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 all three parameters are already documented in the schema; baseline is 3. The description hints at the role of grossMarginPct through the gross-margin-basis framing but adds no format or unit detail beyond the schema.

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: calculating months to recover fully-loaded CAC, and distinguishes two computation bases (gross-margin vs raw-revenue). It does not differentiate itself from nearby siblings such as ltv_cac_calculator or cpa_to_cac_scalability_matrix, so an agent must infer the boundary.

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?

There is no statement of when to use this tool versus the many CAC/LTV-adjacent siblings, nor any prerequisites or exclusions. The only routing context is an external promotional link, which does not help an agent choose between tools.

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