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

The only disclosed behavior is 'Expression discarded', which is a minimal hint that input is not retained. There are no annotations to cover side effects, output behavior, persistence, or whether the operation is read-only, so the description carries the full burden and fails to explain what happens when the tool is called.

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 short and front-loaded, with no wasted words. Brevity is a strength here, though the content is too sparse for the tool's complexity.

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 tool has nine parameters, no output schema, and no annotations, yet the description is only two vague sentences. It does not explain which parameter carries the expression, what the evaluation result looks like, whether results are returned, or how the unrelated schema fields factor in. This is critically incomplete for an agent to invoke correctly.

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 coverage is 100%, which would normally put this at baseline 3, but the description references an 'expression' concept that does not appear anywhere in the schema. None of the nine parameters maps to an arithmetic expression, so the description actively misleads rather than adding meaning beyond the schema.

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 a+b style arithmetic', but the input schema contains no expression parameter and instead lists nine unrelated string fields like url, city, feed, and json. An agent cannot determine what resource the tool actually operates on, and the description does not distinguish this tool from the many sibling shape/ok validators.

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, what conditions select it, or how it compares to alternatives such as domain-shape, validate-json, or search-query-len. With no exclusions or context, an agent has no basis for choosing it over sibling tools.

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