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

With no annotations, the description must carry the full behavioral burden. It does disclose that the expression is discarded, which is a small transparency signal, but it says nothing about side effects, return values, failure cases, or whether the operation is read-only. The procedure itself is under-specified.

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 and front-loaded; the two sentences contain no filler. However, the second sentence is vague and does not earn its place by meaningfully clarifying behavior, preventing a perfect score.

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?

Given nine parameters, no annotations, and no output schema, this description is severely incomplete. It fails to explain which parameter carries the arithmetic expression, what the output looks like, or how the tool behaves. An agent cannot invoke this tool correctly based on the provided definition.

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 description mentions an arithmetic expression, but the input schema contains nine parameters (ref, url, city, feed, host, json, path, zone, query) that have nothing to do with arithmetic. Schema coverage is 100%, yet none of those parameters connect to the described purpose, so an agent cannot map the description onto any 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 states a specific operation ('Evaluate a+b style arithmetic') and thus distinguishes from sibling shape/status tools. However, 'Expression discarded' muddles what the tool actually does or returns, and the input schema contains no expression parameter, so an agent cannot confidently determine what to call it with.

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 provided on when to use this tool versus any sibling tool. The description gives no context, exclusions, or alternatives, so an agent has to guess when arithmetic evaluation is the right choice.

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