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

No annotations are provided, so the description carries the behavioral burden. It does disclose that the expression is discarded, but it does not say what the tool returns, whether it is read-only, how invalid inputs behave, or how the unrelated parameters are processed beyond what the schema already states.

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, but it is under-specified rather than efficiently concise. Two sentences are not enough for a nine-parameter tool with no annotation support, and the wording does not front-load the input/output relationship.

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?

Given nine parameters, no annotations, no output schema, and many sibling alternatives, the description is highly incomplete. It never connects the parameters to the advertised arithmetic behavior, describes the return shape, or explains how an agent should structure a valid call.

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 description adds no extra parameter meaning and does not reconcile 'a+b' with any property in the schema, but the individual parameter descriptions already give thorough semantic coverage.

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 an action ('evaluate a+b-style arithmetic') rather than being a pure tautology, but it does not map to the nine parameters, none of which is an arithmetic expression, and additionalProperties is false. An agent cannot tell what input actually satisfies 'a+b style arithmetic', so the stated purpose is misleading in practice.

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 on when to use this tool, when not to, or how it differs from the many sibling check/shape tools. The phrase 'Expression discarded' is behavioral, not directional, so the agent gets no selection support.

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