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

The description inaccurately lists the third input as 'c' while the input schema defines it as 'x', creating a contradiction. It also fails to disclose any side effects or data modifications, though as a calculation tool, none are expected. The inaccuracy undermines reliability.

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 concise with two sentences and a reference. It is front-loaded with the core purpose and examples. However, the parameter naming inaccuracy slightly detracts from its effectiveness.

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 simple calculator tool, the description covers purpose and usage examples. However, it fails to mention the output format (though an output schema exists per context), and the parameter name mismatch leaves gaps in understanding. It is adequate but not comprehensive.

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 schema already describes parameters with 100% coverage (a: 'Known value A', b: 'Corresponding value B', x: 'New value of A'). The description adds mathematical context ('if a→b, then c→?') but introduces confusion by naming the third parameter 'c' instead of 'x', contradicting the schema and reducing clarity.

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 clearly states the tool solves the rule of three (cross-multiplication) and provides examples like proportions, recipe scaling, and unit pricing. It references list_bundles for related calculators, offering some context among many siblings, but does not explicitly differentiate from other similar calculators.

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 suggests using the tool for proportions, recipe scaling, or unit pricing, which gives clear context. However, it does not provide explicit when-not-to-use guidance or compare with alternatives, though the reference to list_bundles hints at related tools.

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