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

With no annotations, the description carries the full burden of explaining side effects and behavior. It adds only 'Expression discarded', which weakly implies persistence is not an issue, but says nothing about return values, errors, network use, permissions, or whether this is safe to call.

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 only two short sentences with no filler; the operation is front-loaded and the 'discarded' caveat is a compact behavioral note. It is concise, though the brevity comes at the cost of necessary detail.

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?

There is no output schema and no annotations, and the description omits the input mapping and return contract. Given seven unrelated schema fields and no expression parameter, an agent cannot invoke this tool correctly based on the description 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?

The description mentions an arithmetic expression, but the input schema contains no expression, a, or b parameter — only ref, url, city, feed, host, json, and path. None of those fields maps to the a+b expression the description says it evaluates, and the description provides no guidance on where to place the expression. The schema descriptions do not rescue this because they describe entirely different payloads.

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 states a specific operation ('Evaluate a+b style arithmetic'), and no sibling tool obviously covers arithmetic, so some differentiation exists. However, 'Expression discarded' is ambiguous — it could mean the expression is only shape-checked and not computed — and the description never states what the tool returns. An agent cannot be confident whether this produces a numeric result or only validates syntax.

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 this tool instead of a sibling, nor any condition or exclusion. The only implied context is arithmetic evaluation, but nothing explicit helps an agent route to it correctly.

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