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

With no annotations, the description carries the full transparency burden. It adds one behavioral note ('Expression discarded'), but it omits whether a result is returned, what happens with malformed expressions, side effects, or how the nine schema parameters are treated.

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 text is short and front-loaded with the core operation, but it is under-specified rather than efficiently complete. The second sentence adds a behavioral note yet still leaves key selection/invocation details absent.

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 nine-parameter tool with no annotations and no output schema, this description is not usable: it neither says how to supply the expression nor what response to expect. The parameter schema appears to belong to different tools, making correct invocation impossible from the definition alone.

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 adds no parameter guidance and none of the parameters correspond to the promised arithmetic expression. The schema descriptions describe unrelated checks (URLs, city, JSON, etc.), so the mismatch outweighs the schema baseline and leaves invocation ambiguous.

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 first sentence names a concrete operation ('Evaluate a+b style arithmetic'), but the input schema exposes nine unrelated string parameters (ref, url, city, feed, host, json, path, query) with no arithmetic or expression field. An agent cannot tell what this tool actually computes from the definition; the stated purpose does not connect to any parameter.

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?

No when-to-use guidance, prerequisites, or alternatives are given. There is only an implicit 'use when arithmetic is needed,' but nothing distinguishes calc-eval from sibling tools or explains how to route an arithmetic request into the provided parameters.

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