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 safety profile is covered. The description adds genuine behavioral context beyond that: it is a pure deterministic conversion that maps an input percentage to per-day/week/month/quarter/year downtime, or the inverse. It does not explain which inputs take precedence when both directions are supplied.

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 well-formed sentence that front-loads the primary direction (percentage to downtime) before the inverse. Every clause carries information: the accepted input form, the example value, the conversion target, and the period granularity. No filler.

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?

The tool is simple and fully annotated, but with zero required parameters and no output schema, the definition leaves a real gap: it never says what happens if both sla_percent and downtime_hours are provided, or if none are. An agent cannot infer the failure mode or the default direction from the description alone.

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% — every parameter including the period enum and the 99.9/99.95% format example is documented in the schema itself. The description only restates the period list and the percentage example, adding no new semantics such as precedence between sla_percent and downtime_hours. Baseline 3 is appropriate when the schema does the work.

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 dual behavior: converting an uptime percentage into allowed downtime across named periods, or converting downtime length in a period back into an uptime percentage. The resource (uptime/downtime math) and both directions of operation are unambiguous, so an agent can tell instantly whether this is the right tool.

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?

By spelling out both conversion directions, the description implicitly tells the agent which mode applies when it holds a percentage versus when it holds a downtime measurement. It does not state exclusions or prerequisites, but for a self-contained calculator alongside dissimilar siblings (bandwidth_calculator, subnet_calculator), none are needed.

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