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

With no annotations, the description carries the burden; 'Expression discarded' hints at no persistence but does not explain side effects, output, failures, or safety-relevant 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 brief and not padded, but the second sentence creates ambiguity and the overall structure does not clarify the tool's behavior enough to offset the brevity.

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?

The description omits required inputs, expected output, and evaluation semantics; with no output schema and no required parameters, the tool is not sufficiently specified for an agent to invoke correctly.

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?

The tool description adds no parameter-level meaning beyond the schema, and the schema's nine optional string parameters (ref, url, city, feed, host, json, path, zone, query) are unrelated to arithmetic evaluation, leaving callers unable to construct a valid request.

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 action ('Evaluate a+b style arithmetic'), but the second sentence 'Expression discarded' is confusing and the input schema contains no expression parameter, making the actual purpose unclear.

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 is given about when to use calc-eval rather than any sibling tool, nor any mention of conditions or alternatives.

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