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

With no annotations, the description carries the full burden of behavioral disclosure. It does say the expression is discarded, implying no persistence, but it does not explain whether a result is returned, whether any computation side effect occurs, or what an agent should expect after invocation. This is insufficient for a tool with a generic, nine-parameter schema.

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 text is short and starts with the main action, which is structurally positive. However, the brevity omits essential information, and the second sentence, 'Expression discarded,' adds ambiguity without connecting to any schema field. The description is under-specified rather than appropriately concise.

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 optional parameters, no required fields, no annotations, and no output schema, the description is far too incomplete. It does not say how to supply the expression, what a successful evaluation returns, what errors can occur, or any constraints. An agent cannot reliably invoke this tool from the definition alone.

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 the schema documents each parameter individually, the description references an 'expression' that has no corresponding field in the input schema. The actual parameters (ref, url, city, feed, host, json, path, query) are unrelated to arithmetic evaluation, and additionalProperties is false, so an agent cannot pass the expression the description advertises. This actively misleads parameter selection.

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 concrete resource and action: evaluating a+b style arithmetic. This distinguishes the tool from sibling shape/validation tools, but the phrase 'Expression discarded' is ambiguous about what the caller gets, and the schema has no expression parameter that matches the advertised purpose. The overall intent is visible but not fully reliable.

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?

No when-to-use guidance is given, no exclusions are stated, and no sibling alternatives are mentioned. An agent cannot tell when to choose calc-eval over validate-json, search-query-len, or the many other shape/check tools. Usage must be inferred entirely from the tool name and the first sentence.

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