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

The description does not disclose what the tool returns, whether it performs a side effect, or what 'discarded' means. There are no annotations to clarify behavior, so the agent cannot predict outcomes reliably.

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 text is brief and easy to read, but brevity is achieved by omitting essential details. A single vague sentence does not adequately structure the operation, inputs, or outputs.

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 an expression parameter, output schema, examples, and constraints. The schema's unrelated fields and the ambiguous 'discarded' note leave the tool functionally unusable from the description alone.

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 declares nine parameters—ref, url, city, feed, host, json, path, zone, query—but none correspond to the arithmetic expression named in the description. The parameter descriptions appear arbitrary and unrelated to the stated purpose, leaving the agent with no way to supply the required 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 'Evaluate a+b style arithmetic', which identifies a specific verb and object. However, no input parameter for the expression exists in the schema, and the phrase 'Expression discarded' is confusing and unexplained.

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, and no context about expected input format or result. There is no mention of prerequisites, limitations, or typical use cases.

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