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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only states 'Expression discarded', but it does not clarify whether the evaluation result is returned, whether all inputs are discarded, or what the tool actually does with the nine provided parameters. This is insufficient for a tool with no output schema and no annotation safety context.

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 contains no filler, and the key action is front-loaded. However, it is under-sized for a tool with nine parameters and no output schema; it omits essential information while remaining concise.

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 the tool's 9-parameter schema, absent output schema, and complete lack of annotations, this description is grossly incomplete. It does not explain which parameter carries the arithmetic expression, what the tool returns, what 'discarded' means for output, or how this tool relates to the surrounding sibling shape-check 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 description introduces an 'expression' concept that is absent from the schema, so it actively confuses parameter mapping. An agent reading the description would look for an arithmetic expression field, but all parameters are unrelated string fields like host, json, and zone.

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', which names a specific verb and object, but the input schema has no expression parameter at all—only ref, url, city, feed, host, json, path, query, and zone. This means the stated purpose cannot actually be realized from the schema, making the description misleading rather than actionable.

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?

The description gives no guidance about when to use this tool versus alternatives such as validate-json, timezone, normalize-url, or the other sibling shape-check tools. There is also no mention of exclusions or prerequisites, so an agent cannot determine appropriate call conditions.

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