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

The description is consistent with the readOnlyHint annotation; 'Calculate' is a pure read-only computation. However, it does not disclose the formula (cost/clicks), behavior on zero clicks, or return format. Annotations cover the safety aspect, so a baseline score is appropriate.

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 description is a single sentence with zero wasted words. It is front-loaded and directly states the tool's purpose.

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 the schema plus annotation provide decent coverage. However, with no output schema, the description should state the return format (e.g., a number), which it does not. Edge cases like division by zero are also not addressed, but for a simple calculator this is a minor gap.

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?

The input schema fully describes both parameters ('Total cost' and 'Clicks'), and the description adds no additional meaning. The relationship between parameters is implied by 'Cost per click' but not explicitly stated.

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 'Calculate Cost per click (CPC)' uses a specific verb and resource. It distinguishes from sibling calculators like cpm-calculator and ctr-calculator by naming the exact metric, though it lacks additional scope or context beyond the title.

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?

No guidance is provided on when to use this tool versus alternatives. The description does not mention cpm-calculator, ctr-calculator, or any conditions such as 'use when you have cost and click data'.

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