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

Annotations are absent, so the description carries the full burden of behavioral disclosure. It does mention that the expression is discarded, but it fails to clarify return behavior, side effects, required inputs, or auth considerations. The discard note is also attached to an 'expression' that does not appear in the schema, weakening its usefulness.

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 two short sentences with no filler and front-loads the main action. The second sentence is somewhat unclear, but the length and structure are appropriately efficient.

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?

For a tool with nine heterogeneous parameters, no annotations, and no output schema, the description is drastically insufficient. It does not state which parameter to pass, what the tool returns, whether inputs are validated or transformed, or how the arithmetic behavior relates to any of the schema fields.

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, but the description adds no parameter meaning and introduces an 'expression' concept that is not one of the nine schema properties. This can mislead parameter selection instead of helping it.

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'), which is more than a tautology, but it is vague because no schema parameter corresponds to an expression. It also provides no differentiation from the many sibling validator tools, so an agent cannot tell exactly what this tool is for in context.

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 usage guidance is provided: there are no when-to-use conditions, exclusions, or alternatives. The only implied use case is arithmetic evaluation, but the input schema does not support that, and nothing distinguishes calc-eval from siblings like validate-json, normalize-url, or timezone.

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