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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context by clarifying that the tool produces two distinct estimates and warns against a common statistical misinterpretation. This goes beyond the annotations and helps the agent set correct expectations.

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 sentences carry all the essential information: the calculation outputs, the usage trigger, and a statistical caveat. The most important information is front-loaded ('Calculate two different samples'), and every sentence earns its place without redundancy.

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?

Given the presence of a full output schema, rich annotations, and complete parameter documentation, the description covers the remaining contextual needs: what the tool calculates, when to use it, and a key interpretation warning. An agent has everything it needs to select and invoke this tool correctly.

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 schema fully documents each parameter. The description adds some conceptual context by linking failureRate and margin to the two calculation goals, but it does not need to explain parameter syntax or ranges. This aligns with the baseline 3 for high schema coverage.

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 verb ('Calculate') and resource ('two different samples' of evaluations), and clearly defines what the two samples are for: detecting at least one failure and estimating the failure rate at a chosen margin. This is distinct from the sibling calculation tools and leaves no ambiguity about the tool's core function.

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?

The description gives an explicit usage condition: 'Use this when a user asks how many tests are enough.' It also provides a critical interpretive guardrail ('do not interpret zero observed failures as proof of zero risk'). It does not explicitly name alternatives or state when not to use it, but the context is clear enough for an agent to route appropriately.

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