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 little beyond that: it restates inputs and outputs already present in the schema/output schema, and mentions no determinism caveats, unit assumptions, or limitations. Some value is added by framing it as a pure SaaS metric calculator.

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, purpose front-loaded, no padding. The closing bundle pointer is marginally useful but slightly off-topic for selecting this tool. Efficient overall.

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 an output schema present, the description need not explain return values, and it correctly sketches inputs, purpose, and domain fit. A deterministic read-only calculator of this complexity is adequately covered; only the missing 'customer vs revenue' clarification leaves a minor gap.

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 the baseline is 3. The description lists 'starting customers, churned, period length' which mirrors the three schema parameters but adds no format, unit, or edge-case detail (e.g. what period_months defaults to, or that churn is computed against start_customers).

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 (compute churn rate) plus scope (customer or revenue, over a period) and a domain (SaaS). Clear enough to distinguish from generic math siblings, though it does not explicitly name a competing sibling like calculate_burn_rate or calculate_cac_ltv_ratio. The 'revenue churn' claim is slightly loose given the schema only accepts customer counts.

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?

'Use for SaaS retention analysis' gives an implied use case but no when-not conditions and no named alternatives. The list_bundles reference points at a bundle-discovery tool rather than a competing calculator, so it does not help the agent choose between this and sibling finance metrics. Adequate but thin.

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