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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the agent knows this is a safe, deterministic, offline computation. The description reinforces this by describing a pure back-calculation and discloses the 3:1 default ratio. It stops short of describing the shape of the result (single number, per-currency formatting), which the missing output schema leaves to inference.

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?

A single dense sentence with the core operation front-loaded ('works back from customer lifetime value') followed by the outputs and the default ratio. No preamble and no wasted clauses.

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 six-parameter, no-output-schema calculation tool, the description conveys the input concepts (LTV inputs, target ratio, optional lead conversion) and the outputs conceptually (max CAC, max cost per lead). Given 100% schema coverage and strong annotations, a 4 is warranted; only the concrete return format is left implicit.

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 every parameter is already documented in the schema. The description adds a small amount of meaning by tying the target ratio to the '3:1 default' and flagging that the lead metric is optional, but it introduces no syntax or modeling detail beyond the structured fields. 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 states a specific calculation: deriving the maximum affordable CAC (and optionally cost per lead) from LTV and a target ratio. An agent can immediately tell this is a unit-economics calculator rather than a general metric tool. It does not explicitly distinguish itself from siblings like customer_lifetime_value or unit_economics, but the verb+resource is unambiguous.

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 use case is implied by the framing (working back from LTV to a CAC ceiling), and the mention of an optional lead calculation signals a variant. However, there is no explicit when-to-use guidance, no statement of prerequisites, and no pointer to the closely related siblings (customer_lifetime_value, unit_economics, break_even) that an agent would need to choose correctly.

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