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

No annotations are provided, and the description is misleading: it claims the expression is discarded but no expression parameter exists. It also does not disclose side effects, persistence, failure behavior, or what the tool returns.

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 the second sentence 'Expression discarded' is confusing and tied to no parameter. The brevity comes at the cost of clarity rather than efficient communication.

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 no output schema, no annotations, and nine seemingly unrelated optional parameters, the description is far too incomplete for an agent to know what to pass or what result to expect.

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 adds no meaning to the nine parameters. Each schema description appears unrelated to arithmetic (e.g., 'Git ref name', 'IANA timezone name'), and the top-level description never maps the parameters to an arithmetic expression or result.

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 says 'Evaluate a+b style arithmetic' but the schema contains no expression or arithmetic parameters; instead it lists ref, url, city, feed, host, json, path, zone, and query. The phrase 'Expression discarded' contradicts the apparent action and does not identify what the tool actually does or how it differs from sibling tools.

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 guidance is given on when to use this tool versus alternatives. The description does not explain what input the agent should provide, what conditions favor this tool over siblings, or what the expected usage pattern is.

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