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

With no annotations, the description must carry all behavioral disclosure. 'Expression discarded' hints at side effects but does not explain what happens to the nine parameters, what the tool returns, or any constraints. The mismatch between the description and schema further obscures behavior.

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 short but that is under-specification rather than conciseness. One vague sentence provides no actionable information, and it is not front-loaded with a clear scoping statement.

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 nine heterogeneous parameters, no required fields, and no output schema, this description is wholly inadequate. An agent cannot infer what inputs to provide, what to expect in return, or how it relates to the sibling tools.

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 coverage is 100%, the tool description adds zero meaning to any parameter. It never mentions ref, url, city, etc., and the arithmetic phrasing does not map to any parameter. The description fails to compensate for the disconnect between its stated purpose and the actual input.

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 says 'Evaluate a+b style arithmetic' but the input schema has nine unrelated parameters (ref, url, city, feed, host, json, path, zone, query) with no arithmetic operands. The purpose is unclear and contradicts the actual interface; it does not state what the tool does with these parameters.

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 guidance on when to use this tool versus any of the 27 siblings. The description gives no context, no alternatives, and no exclusions, leaving an agent unable to decide when to invoke it.

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