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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds two meaningful bits beyond that: the non-negative input constraint (a validation behavior) and the fact that it returns the canonical web tool URL. It stops there, adding nothing about the calculation method or bounds.

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 tight sentences with the verb front-loaded and zero filler; the return behavior is stated second where it belongs. It is well-sized, though the second sentence is somewhat generic.

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 spelled out, and the tool is a simple arithmetic operation. Yet with 0% parameter description coverage, an agent still cannot tell what each of the three counts means or how they combine, leaving the definition only marginally 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 0%, so the description carries the full burden. It only broadly labels the inputs as 'non-negative counts' and hints at 'signup and conversion rates,' giving no per-parameter meaning, no indication that conversions is optional, and no explanation of how visits and signups relate to the computed rates.

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 and resource: 'Calculate ... signup and conversion rates.' This is clearly distinguishable from siblings like launch_readiness or relaunch_decision. However, it never explicitly differentiates itself from the other launch-oriented tools in the set, so it stops short of a 5.

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 explicit when-to-use or when-not-to-use guidance, and no sibling is named as an alternative. The only usage signal is the passing implication that the caller supplies the counts, which is not real routing guidance.

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