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

With no annotations, the description carries full behavioral burden but discloses only that the tool relates diameter to ear appearance. It does not state that the operation is read-only, deterministic, or what kind of output (string, score, image) is produced, leaving key behavioral traits unstated.

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?

A single, front-loaded sentence with no filler. It is appropriately terse for the tool, though the extreme brevity contributes to the specification gaps noted elsewhere.

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?

For a one-parameter tool with no annotations, no output schema, and 0% schema coverage, the description should explain what the tool returns and when to use it. It does neither, leaving the agent without enough context to invoke confidently.

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 single parameter has 0% schema description coverage, so the description must compensate. It clarifies that the input is the stone diameter (not ear or setting), which is a meaningful addition, but omits any range, precision, or expected units beyond what the name 'diameter_mm' implies.

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 identifies the subject (a round stud, given stone diameter, on the ear) but offers no explicit action verb or output type; 'reads on the ear' is metaphorical, so an agent cannot be certain whether it returns a size comparison, text description, or visual estimate. It is distinct from siblings only by domain implication, not explicit differentiation.

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 when-to-use guidance or alternatives are stated. The phrase 'on the ear' implies an earring context but does not tell the agent when to choose this over ring_size_convert, necklace_length, or the mm/carat converters.

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