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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so the safety profile is fully covered structurally. The description adds only the list of computed outputs; it discloses nothing about the formulas, assumptions (e.g. how churn converts to lifetime), or rounding behavior. Adequate but thin for an analytical tool.

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 short sentences, front-loaded with the computation, so the core information arrives immediately. The trailing external URL is mildly promotional filler that does not earn its place in a tool definition.

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 five required parameters fully documented in the schema and no output schema, the description does the important complementary job of naming the four returned metrics. It is close to complete, though it omits period-assumption details that matter for a calculation tool.

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 five inputs are documented in the schema itself, giving a baseline of 3. The description adds no parameter-level meaning, units convention, or period-alignment guidance 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 a specific verb (calculate) and enumerates the exact outputs: customer LTV, CAC, the LTV:CAC ratio, and CAC payback period. That is clear and concrete, but it never distinguishes itself from close siblings like cac_payback_period_matrix or ltv_to_cac_ratio_health_grader, which an agent could easily confuse it with.

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 alternative LTV/CAC/payback tools in the sibling list, and no prerequisites or input-period guidance. The only extra sentence is a promotional pointer to an external site, which does not help selection.

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