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

With no annotations provided, the description must fully disclose behavior. The only behavioral statement is 'Expression discarded,' which is cryptic and does not clarify side effects, permissions, return values, or what happens to the input parameters. For a tool with such a vague description, this is severely inadequate.

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 a single sentence, which is concise, but it is under-specified and does not convey essential information. It front-loads a purpose that contradicts the schema, making the brevity counterproductive.

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 tool with 9 optional parameters, no required parameters, and no output schema, the description must provide context on how parameters are used, what the evaluation does, and what the caller should expect. The description is wholly inadequate, leaving an agent with no way to correctly invoke the tool.

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% in that every parameter has a schema description, but the tool description adds no meaning beyond the schema. The parameters (ref, url, city, feed, etc.) appear unrelated to the stated arithmetic purpose, and the description does not explain their role or how they relate to evaluation. It adds no value over the schema and fails to resolve the mismatch.

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 'Evaluate a+b style arithmetic,' which is a clear verb+resource, but the input schema contains nine parameters (ref, url, city, feed, etc.) that have no relation to arithmetic expressions. There is no parameter for the expression itself, making the stated purpose incompatible with the actual schema. The purpose is stated but misleading.

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 on when to use this tool versus the many siblings (weather-hint, normalize-url, validate-json, etc.). The description provides no context for which scenarios this tool fits, nor does it mention any exclusions or alternatives.

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