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

With no annotations, the description carries the full burden. It only says 'Expression discarded', which is ambiguous and does not clarify whether results are returned, side effects, or error 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 very brief and front-loaded, but the second sentence 'Expression discarded' adds confusion rather than clarity. It is concise but not effectively structured.

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 lacks essential context: no explanation of how parameters relate to the calculation, no output schema, no return value description, and no usage context. The schema mismatch makes the tool's actual behavior nearly impossible to infer.

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 schema parameters (ref, url, city, feed, host, json, path, zone, query) are completely unrelated to arithmetic evaluation, and their descriptions ('discarded after the shape check', etc.) do not add meaningful semantics for a calc-eval tool.

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 it evaluates 'a+b style arithmetic', which identifies a basic purpose, but no parameter in the schema corresponds to an expression or operands. The intended function is therefore unclear and inconsistent with the provided parameter set.

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 for when to use this tool versus any sibling tool. It does not mention alternatives, prerequisites, or typical scenarios.

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