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

With no annotations, the description carries the full behavioral burden, but it discloses only that the expression is discarded. It does not state what the tool returns, whether it performs real computation, what a valid a+b input looks like, or what happens when validation fails.

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 short and front-loaded, but it is under-specified to the point of ambiguity. The two sentences do not form a coherent specification of what the tool accepts or returns, so brevity here comes at the cost of usefulness.

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 9-parameter tool with no annotations and no output schema needs a much richer description. This one fails to explain return values, how the many discardable parameters relate to arithmetic evaluation, or any error semantics, making correct invocation effectively impossible.

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?

Schema description coverage is 100%, so the baseline is 3 even though the description contributes no parameter-level detail. The description references an 'expression' that does not exist among the nine schema properties, so it adds no clarifying meaning to the actual 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 operation, evaluating a+b style arithmetic, which is more than a tautology. However, it never ties this operation to any field in the input schema, and there is no expression parameter an agent could populate. The phrase 'Expression discarded' also leaves ambiguity about whether the tool returns a result or merely validates and forgets the input.

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 when-to-use guidance, no criteria for choosing this tool over alternatives, and no mention of sibling tools. The discard note is a behavioral observation, not actionable guidance about when calc-eval should be invoked.

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