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

With no annotations present, the description must fully disclose behavior, but it only says ROI is calculated from invested and returned amounts. It does not reveal whether the result is a percentage or ratio, how the other six fields (cost, gain, final, years, current, initial) are handled, or what output to expect.

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 short and front-loaded: it states the operation before instructing which values to provide. The leading label 'ROI Calc:' is mildly redundant with the tool's purpose, and the description could have used the space to clarify the extra parameters.

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?

Against the context of 8 optional string parameters, no output schema, and no annotations, the description is under-specified. It tells the agent to supply invested and returned, but gives no information about the remaining fields, the result format, or input formatting, so an agent could mis-invoke the tool if it guesses about the additional parameters.

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%, but each parameter description is a generic 'X to process'; the description adds only the clarification that invested and returned are the core amounts. The other six parameters remain semantically unexplained and are neither mapped to a mode nor marked as ignored, so the description adds only marginal meaning.

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 concrete operation—calculate Return on Investment—and names the two inputs (invested and returned amounts) that define it, making the tool's purpose clear. It does not distinguish this from sibling tools such as x402-roi, so it misses the top score.

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?

"Provide invested and returned values" is explicit guidance on what an agent should supply, which matters because the schema has eight optional parameters. It does not state when to prefer this over related siblings or explicitly exclude the other parameters.

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