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

With no annotations, the description carries the full burden of disclosing side effects. It does disclose that an expression is discarded, which hints at non-persistence, but it omits return behavior, error conditions, and whether any computation result is produced at all.

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 extremely short with no filler or redundant schema repetition. However, the second sentence is ambiguous, so it is efficient but not perfectly clear.

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 parameters, no annotations, and no output schema, this description is too thin to support correct invocation. It does not state return values, which parameter if any is the expression, or what 'discarded' means for the agent's expected result.

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; the schema already documents all nine string parameters in detail. The description adds no parameter meaning and actually creates a mismatch by referencing an expression parameter that is absent from the schema.

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 gives a verb ('Evaluate') and a resource ('a+b style arithmetic'), but it is nearly a restatement of the tool name and does not specify which input carries the expression. The sentence 'Expression discarded' actively undermines the stated purpose, and no schema property maps to an arithmetic expression.

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 guidance about when to choose this tool over any sibling or when not to use it. The only contextual hint is 'Expression discarded,' which gives no information about prerequisites, intended call patterns, or alternatives.

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