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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds domain-meaningful context beyond that: the interpretation threshold (target ≥3.0) and the fact that a health verdict accompanies the ratio. It omits edge-case behavior (e.g. LTV=0), keeping it from a 5.

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?

Four short sentences, front-loaded with the core computation before usage, inputs, and output. The 'Inputs:' sentence mildly duplicates the schema and the bundle pointer is incidental, so it is efficient but not maximally tight.

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 2-parameter read-only calculator with a 100%-covered schema, an output schema, and full annotations, the description supplies the one thing structured fields cannot: the domain benchmark for interpreting the result. Nothing an agent needs to invoke it correctly is missing.

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 both cac and ltv documented including EUR units, so the schema carries the semantic load. The description only restates them as 'Inputs: total CAC, LTV' and adds no format or constraint detail, matching the baseline 3.

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 (Compute) and a precise resource (CAC vs LTV ratio), and the acronym is spelled out so an agent knows exactly what is calculated. It is readily distinguishable from neighbor tools like calculate_churn_rate or calculate_roi.

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?

Gives clear context ('Use for SaaS unit economics analysis') and even a benchmark target (≥3.0), so the agent knows when this applies. It does not name a competing tool or state exclusions, and the pointer to list_bundles is about discovery rather than a true alternative, so it falls short of a 5.

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