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

With no annotations, the description carries the full burden, but it only states that the expression is discarded. It does not disclose whether the operation is read-only, what evaluation result is returned, whether any input is persisted, or what errors occur.

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 very short and front-loaded with the main action; there is no filler. Brevity is gained at the cost of clarity, but conciseness itself is effective.

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 unrelated parameters, no annotations, and no output schema, this two-sentence description is far from complete. It omits return behavior, parameter mapping, side effects, and failure modes.

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 coverage is 100% and each property has its own description, the tool description never explains which of the nine fields should contain the arithmetic expression—or whether any of them do. The 'a+b' concept is disconnected from the schema, so an agent cannot reliably determine what to pass.

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 concrete action ('Evaluate a+b style arithmetic') and a clear resource, which separates it from sibling validation/checking tools. However, it does not connect the expression to any of the nine input schema fields, and 'Expression discarded' muddies what the tool ultimately returns.

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?

Usage is only implied by the phrase 'a+b style arithmetic' rather than stated with conditions or alternatives. No when-to-use/when-not-to-use guidance is given relative to the many sibling tools, so an agent must infer applicability.

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