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 fully covered without the description. Beyond the word 'Calculate,' the description adds no behavioral context such as how usedDowntimeMinutes affects the result, whether the budget is purely derived, or any constraints on inputs.

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?

The single sentence is front-loaded and free of padding, which is good structure. It is, however, under-specified rather than concise: there is room for one more sentence clarifying inputs and the latency_budget distinction at no cost to readability.

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?

An output schema exists, so return values need not be explained, but that is the only gap covered. With three required, zero-documented parameters and a highly similar sibling tool, the definition leaves an agent guessing about input meaning and tool selection.

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 0% for all three required parameters, so the description must compensate and does not. Only 'availability' and 'period' loosely gesture at availabilityPercent and periodDays, while usedDowntimeMinutes — the semantically important input that presumably reduces the remaining budget — is left entirely unexplained.

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 and resource ('Calculate an availability error budget'), so the agent knows exactly what operation is performed. It does not, however, distinguish itself from the sibling latency_budget, which an agent could easily confuse with this one at selection time.

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 guidance on when to use this versus latency_budget or capacity_plan, and no prerequisites or exclusions are stated. The only usage signal is the vague phrase 'for a chosen period,' which the agent must infer.

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