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

No annotations are provided, so the description should carry the full load of behavioral disclosure. The phrase 'Expression discarded' is not meaningful since no expression parameter exists; it does not say whether the tool mutates state, returns a result, or why inputs are discarded.

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, but brevity is not useful when it sacrifices clarity. The second sentence, 'Expression discarded,' is confusing and does not earn its place; a short but misleading description is worse than a longer, clear one.

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 9 parameters, 0 required, no annotations, and no output schema, the description is critically insufficient. An agent has no way to infer the intended input or whether this is the right tool for a task.

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 has 100% description coverage, but the tool description adds no parameter-level value and actually misrepresents the interface by implying an expression parameter that is not present. An agent cannot map the arithmetic use-case onto any of the nine named string parameters.

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 claims 'Evaluate a+b style arithmetic,' but the input schema defines no arithmetic expression parameter. All nine parameters (ref, url, city, feed, host, json, path, zone, query) are described as being discarded or checked, so the tool's actual purpose is opaque and likely misleading for an agent looking to perform arithmetic.

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 guidance on when to use this tool versus the many siblings like web-fetch, normalize-url, or validate-json. No conditions, prerequisites, exclusions, or examples are given.

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