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

The phrase 'Expression discarded' partially discloses behavior, but it is vague and contradicts the stated purpose. No other effects, side effects, authentication, or error behavior are disclosed, and there are no annotations to supplement.

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 (one sentence), which is appropriately concise, but it sacrifices clarity. It does not waste words, yet it fails to convey essential information about the tool's operation.

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?

No information is provided about the return value, output format, error cases, or how the tool interacts with the given parameters. The lack of an output schema and the ambiguity of the description leave the agent with insufficient context.

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?

Though the schema covers all parameters with individual descriptions, the tool description adds no meaning to them. The parameters (ref, url, city, etc.) appear unrelated to arithmetic evaluation, and the description does not explain how they are used, making the parameter list confusing.

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 clearly identifies a verb and resource, but it immediately adds 'Expression discarded' and the input schema contains no expression-related parameters. This makes the actual purpose ambiguous and 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 indication of when to use this tool versus any alternative. The description does not mention use cases, prerequisites, or situations where this tool is preferred, leaving the agent without guidance.

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