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

Annotations are absent, so the description carries the full burden. It only says 'Expression discarded,' which is confusing because no expression parameter exists. No disclosure of side effects, authentication requirements, rate limits, or what the tool does with the actual parameters.

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 brevity is not conciseness here – it under-specifies the tool. The single sentence provides no actionable structure or front-loaded context, and it actively misleads about the tool's function.

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 nine optional parameters, no output schema, and no annotations, the description is grossly incomplete. It fails to explain what the tool actually does with any of the parameters, how results are returned, or any constraints. An agent has no reliable basis to invoke it correctly.

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 coverage is 100%, but the description adds zero meaning to the parameters. Worse, the description's mention of arithmetic contradicts the schema's fields, which are unrelated to arithmetic. An agent cannot infer how 'ref', 'city', or 'json' relate to the tool's purpose.

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 claims to evaluate 'a+b style arithmetic' but the input schema contains nine unrelated parameters (ref, url, city, feed, host, json, path, zone, query) with no expression parameter. This is misleading – an agent would expect an arithmetic expression input but finds none, and the purpose is entirely unclear relative to the actual schema.

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 provided on when to use this tool versus any of its 27 siblings. There is no mention of context, alternatives, or exclusions, leaving the agent to guess which tool fits the task.

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