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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is fully covered. The description adds that the result includes relative uplift and statistical confidence, which is genuinely useful given there is no output schema, but it omits test assumptions and any caveats about validity.

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 short sentences, with the core operation and outputs front-loaded before the external link. The second sentence contributes little to invocation correctness, but the total length is small enough that waste is minimal.

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 pure four-number computation with fully documented parameters and clear safety annotations, the description is sufficient: it names the test performed and the two result values returned. Only the absence of statistical assumptions or a hint at the response format keeps it from being fully complete.

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% and each of the four parameters is documented as visitors/conversions for control vs test variants. The description adds no additional parameter meaning, so the baseline of 3 applies.

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 precise statistical operation (two-proportion z-test) on a specific input domain (an A/B test) and names its outputs (relative uplift, statistical confidence). No sibling tool performs significance testing, so the name and verb effectively distinguish it, though the description never says so explicitly.

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 other calculators, no prerequisites (e.g., minimum sample size, one- vs two-tailed test), and no exclusions. The trailing external link is promotional rather than a routing cue.

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