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

With no annotations, the description carries the full burden of disclosing behavior. It offers one signal ('Expression discarded') but does not explain what is discarded, whether a result is returned, how errors are handled, or whether the operation is read-only; 'Evaluate' and 'discarded' even pull in opposite directions.

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 very short and fronts the purpose, but the second sentence is cryptic and adds confusion rather than clarity. This is under-specification, not effective conciseness.

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?

With nine optional parameters, no output schema, and no annotations, the description is far too incomplete. It fails to specify the input parameter, the return value, or the behavior, so an agent cannot reliably select arguments or interpret the result.

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 schema description coverage is 100%, the description introduces an 'a+b style arithmetic' concept that maps to none of the nine parameters (ref, url, city, feed, host, json, path, zone, query). It gives the agent no help choosing which parameter holds the expression, and the schema does not contain one.

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 names a specific operation ('Evaluate a+b style arithmetic') that distinguishes it from sibling shape-check tools. However, the phrase 'Expression discarded' makes it unclear whether the tool returns a result, validates the expression, or simply discards it, and no arithmetic-expression parameter appears in the schema.

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 usage context is given beyond the terse purpose. It does not state when to prefer calc-eval over alternatives, nor any exclusions, so an agent must guess when this tool is the right choice.

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