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

With no annotations, the description must carry the full burden, but it only mentions a non-existent 'expression' that is 'discarded'. There is no disclosure about side effects, return format, or what the parameters actually do. The description is actively misleading since it references an 'a+b style arithmetic' that has no schema representation.

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 (one sentence), which is concise, but it is misleading and does not earn its place. It provides no useful information about the tool's actual functionality, so brevity is not a virtue here.

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?

This tool has 9 parameters, no required fields, no output schema, and no annotations. The description offers no context about what the tool does, what the parameters mean, or what the return value looks like. It is grossly incomplete for a tool with this complexity.

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?

Although schema description coverage is 100%, the description adds zero value to parameter understanding. It doesn't explain any of the 9 parameters or their relationship to the supposed arithmetic operation. The description contradicts the schema, so it fails to clarify parameter semantics.

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 input schema contains 9 parameters (ref, url, city, feed, host, json, path, zone, query) with no arithmetic-related field. The stated purpose does not match the schema at all, leaving the agent unable to determine what this tool actually does.

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 on when to use this tool versus any of the 27 siblings. The description does not provide any context for selection, and the mismatch between description and schema makes it impossible to infer appropriate usage.

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