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

With no annotations, the description carries the full burden for behavioral disclosure. Saying 'Expression discarded' hints at non-retention, but it says nothing about whether the tool is read-only, what it returns, error behavior, or side effects. Most behavioral traits an agent would need are unstated.

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 contains no filler, but it is under-specified rather than effectively concise. The second sentence, 'Expression discarded', is ambiguous and does not clarify the tool's input or output enough to earn its place.

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?

With nine parameters, no output schema, and no annotations, the description is severely incomplete. It fails to explain the invocation pattern, the role of each parameter in the arithmetic operation, or the return value, so an agent cannot safely call the tool.

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%, which normally supports a baseline of 3. However, the description introduces an arithmetic 'expression' that maps to none of the nine parameters, and it does not connect any schema field to the a+b operation. This mismatch lowers the semantic value below the baseline.

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 specific action, 'Evaluate a+b style arithmetic', so it goes beyond a tautology. However, it does not explain how the expression is supplied, and the nine-parameter schema contains no expression or operand field, making the stated purpose hard to act on. It also does not differentiate itself from any sibling tool.

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 use calc-eval versus any sibling tool. The only implied usage is 'for arithmetic evaluation', but no exclusions, prerequisites, or alternative tool references are provided.

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