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

With no annotations provided, the description must carry the behavioral burden. It says "Expression discarded," which at least hints the input is not returned, but it does not explain what is returned, whether this is a pass/fail check, or whether it has side effects. The mention of "expression" conflicts with the schema, making the actual behavior even less transparent.

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 extremely concise and front-loaded, earning points for brevity. However, the second sentence "Expression discarded" is imprecise (no schema param named expression) and arguably not an earned sentence because it adds confusion rather than clarity.

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?

This is a tool with 9 optional parameters, no annotations, and no output schema, so the description needs to explain what inputs to provide and what outcome to expect. It only says "Evaluate a+b style arithmetic” and “Expression discarded”, covering none of the actual parameters and no return behavior; this is severely incomplete.

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%, so the baseline is 3, but the description introduces a phantom "expression" that has no corresponding parameter in the schema. It adds no clarifying value for the actual parameters like ref, url, city, or query, and instead likely misleads an agent into looking for an input that does not exist.

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?

"Evaluate a+b style arithmetic" states a verb and resource, but it does not connect to any parameter in the 9-parameter input schema (there is no expression parameter). It also does not distinguish itself from sibling shape/check tools, and the phrase "Expression discarded" muddies whether it returns a result.

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 guidance about when to use this tool versus any sibling tools, and no mention of conditions, exclusions, or alternatives. The only extra sentence is a behavioral note, not usage guidance.

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