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

No annotations are provided, so the description must carry the full burden. It only says 'Expression discarded' which is cryptic and does not explain the tool's overall behavior, side effects, or return value. It fails to disclose that the tool accepts multiple input types and discards them after checks, and it does not state what happens on invalid input.

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 one sentence, which is concise, but it is so underspecified that it does not earn its place. It lacks essential information about the tool's purpose and parameters, making it an ineffective use of even that short length.

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 9 parameters, no annotations, and no output schema, a complete description is essential. This one-sentence description provides almost no context: it does not explain the tool's overall function, what it returns, or how to choose parameters. An agent cannot correctly invoke this tool based on this 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 schema provides 100% description coverage for all 9 parameters, so the baseline is 3. However, the description's focus on 'a+b style arithmetic' does not map to any of the parameters, which are named ref, url, city, etc. This mismatch actively misleads the agent about how to fill parameters, so the description adds no value and reduces clarity.

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 'Evaluate a+b style arithmetic' which names a specific verb and resource, but it is misleading because the input schema contains 9 unrelated parameters (ref, url, city, feed, etc.) with no arithmetic operands. It also says 'Expression discarded', which contradicts the idea of evaluation. It does not differentiate from sibling tools like 'compatibility' or 'domain-shape'.

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 on when to use this tool versus alternatives. The description does not mention any prerequisites, conditions, or exclusions. An agent has no idea whether to call this for arithmetic, URL checking, or timezone validation.

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