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

With no annotations provided, the description carries the full burden of behavioral disclosure, but it only says 'Evaluate a+b style arithmetic. Expression discarded.' This is cryptic and does not explain what the tool actually does with the nine parameters, what side effects occur, or what the return value is. The schema descriptions ('discarded after the shape check') hint at validation, but the description contradicts that by implying arithmetic evaluation.

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 extremely short, but conciseness is not the issue—it is under-specification. The single sentence provides no actionable structure or key information; it wastes the reader's time by claiming arithmetic evaluation while the schema shows a different set of inputs.

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?

Given nine optional parameters, no required fields, and no output schema, the description is grossly incomplete. It does not explain the tool's actual function, how to choose parameters, what the return format is, or when to use it. An agent has almost no chance of correctly invoking this tool 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?

Schema coverage is 100%, so the baseline is 3, but the description actively misleads by implying an 'expression' input that does not exist in the schema. It adds no meaning to the actual parameters (ref, url, city, etc.) and fails to connect them to the stated purpose, making the tool harder to use correctly rather than easier.

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 verb and resource ('Evaluate a+b style arithmetic'), but it is misleading because the input schema contains no expression parameter—instead listing nine unrelated optional parameters like ref, url, city, and feed. This mismatch confuses rather than clarifies what the tool actually does, so it falls short of a clear purpose statement.

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?

The description gives no guidance on when to use this tool versus the many siblings (e.g., normalize-url, validate-json, search-query-len). It neither states typical use cases nor excludes alternatives, leaving the agent to guess based on the misleading name and description.

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