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

Annotations only cover readOnlyHint and openWorldHint, so the description usefully adds that each call costs 60 points and enumerates what is returned. Since there is no output schema, disclosing the return fields and the explicit non-provision of emission grade is meaningful behavioral context beyond the annotations.

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 English sentence front-loads the purpose, and the Korean text adds the field list, exclusions, and cost. The field enumeration is long but justified because no output schema exists. Structure is clean with minimal waste, though the enumeration is denser than strictly necessary.

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 no output schema, the description carries the return-value burden and does so by listing all returned fields, plus cost and input-key constraints. Safety is covered by annotations. Missing only edge details such as what happens on an unknown cert_no or any pagination/history limits.

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 description coverage is 100% and the single parameter is documented with an example, so the baseline is 3. The description adds value by explicitly clarifying that cert_no is the emission certification number and not the vehicle registration number, disambiguating a common confusion beyond what the schema states.

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 precise verb ('look up') and a very specific resource (Korean vehicle emission certification details) and enumerates the exact fields returned, which makes the scope unambiguous. It does not explicitly name a sibling like vehicle_model_info, so it falls short of the 'distinguishes from siblings' bar for a 5, but the resource specificity effectively separates it from other vehicle tools.

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?

It gives clear conditional guidance: the input key is the emission certification number, NOT the vehicle registration number, and the emission grade is not provided. These are genuine when-to-use exclusions. However, no alternative tool is named for the grade-related case, so it stops short of full when/when-not/alternatives coverage.

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