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

With no annotations, the description carries the full burden of behavioral disclosure. It offers only 'Expression discarded,' which is confusing rather than informative, and omits what the tool returns, side effects, or prerequisites. It also contradicts its own schema by referencing an expression input that does not exist.

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 definition is short, but the brevity here is under-specification, not conciseness. The second sentence repeats a confusing discard notion, and important information such as input mapping and return behavior is absent.

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?

A nine-parameter tool with no annotations and no output schema needs substantial behavioral and mapping context. The two-sentence description leaves an agent unable to form a correct call, making it critically incomplete.

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 description coverage is 100%, the tool description fails to connect 'a+b arithmetic' to any of the nine parameters. An agent cannot tell which parameter contains the expression, so the description actively undermines otherwise documented 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 names a concrete action ('Evaluate a+b style arithmetic'), but the input schema contains no expression parameter and instead lists nine unrelated strings like ref, url, city, and query. The phrase 'Expression discarded' further muddles what the tool actually computes, so an agent cannot determine what resource is operated on.

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 when-to-use or when-not-to-use guidance is provided. The description never names an alternative, states conditions, or references the many sibling tools, leaving the agent without any basis for choosing this tool over others.

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