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 says 'Expression discarded,' which hints at a side effect but gives no detail about what the tool actually does with the input, what it returns, or whether it performs any real computation. The mismatch with the schema compounds the opacity.

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 extremely short, but this is under-specification rather than conciseness. It consists of two fragments that do not explain the tool's purpose or usage. Every word is wasted because it describes behavior that the schema does not support.

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 tool has nine parameters, no required fields, no output schema, and no annotations. The description provides almost no context about what the tool does, what inputs are meaningful, what the result looks like, or when to use it. This is grossly inadequate for an agent to invoke the tool correctly.

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 the schema has 100% description coverage for its nine parameters, the tool description does not reference any of them. The phrase 'a+b style arithmetic' does not map to any schema property, so the description adds zero meaning and actually contradicts the schema's content. This fails to compensate for any gap and introduces confusion.

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 action ('Evaluate a+b style arithmetic') but it is entirely disconnected from the input schema, which contains unrelated parameters like url, city, and feed. This is not a tautology, but it is misleading because the described behavior does not match the actual tool interface, and it does not distinguish the tool from its many siblings.

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 provides no guidance on when to use this tool versus alternatives. It does not mention any context, prerequisites, or exclusions. An agent would have no way to know if this tool is appropriate for a given task or how it relates to sibling tools like timezone or validate-json.

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