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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds real context: a fixed operator/function allowlist, the deliberate avoidance of math.js evaluate(), and the fact that it doesn't spend points or accept URLs. It stops short of saying what happens on a disallowed operator or what the return value looks like.

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?

Three short sentences, front-loaded with the core action and followed by the two constraints. The math.js rationale is slightly extraneous but justifies the boundedness claim, so it earns 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?

For a simple one-parameter tool with no output schema, the description is mostly adequate, but it omits any hint of the result shape (number vs string) and the error behavior for rejected expressions, leaving an agent to discover these at call time.

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 0% for the single expression parameter, so the description must compensate. It conveys that only one expression is taken and implies bounded syntax via the allowlist, but never enumerates allowed operators or functions, so the caller still has to guess at valid input.

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?

States a specific verb+resource: 'evaluate one expression' for bounded arithmetic. It doesn't explicitly differentiate from siblings, but no sibling is an arithmetic tool, so the purpose is unmistakable.

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 implied by 'evaluate one expression,' and the negative constraints ('does not spend points and does not accept a URL') steer away from wrong expectations. However, there is no explicit statement of when to reach for this tool versus alternatives or what to do if an expression is rejected.

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