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

With no annotations, the description carries the transparency burden. It does disclose one meaningful behavior: the expression is discarded, implying no persistence. But it does not disclose the return value, error behavior, or whether the other schema parameters participate, so the disclosure is only partial.

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, front-loaded, and free of filler, but it is under-sized for a 9-parameter tool. The cryptic 'Expression discarded' phrase and the lack of any connection to the schema make it less appropriately sized than truly concise.

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 has 9 optional parameters, no annotations, and no output schema, so the description must carry the load. It provides a clear purpose and a discard note, but leaves the main input unmapped and says nothing about the result, making correct invocation impossible from the definition as given.

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?

Although all nine schema parameters have descriptions, none of them represents an arithmetic expression. The description's key input—'expression'—has no mapped schema property, so an agent cannot know where to put '2+2'. This is actively misleading rather than additive.

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 action ('Evaluate') and a specific resource ('a+b style arithmetic'), making the tool's core purpose clear. It also distinguishes this tool from the many sibling shape-checkers and normalizers, since no sibling is described as an arithmetic evaluator.

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 opening phrase implies the tool should be used when an agent needs to evaluate simple arithmetic, so there is implied usage guidance. However, it never states exclusions, prerequisites, or when to prefer a sibling tool, leaving the routing decision mostly to inference.

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