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

The description discloses that definitions are reworded compilations from open/public sources, that it never guesses, that descriptions are not verbatim, and that severity is not guaranteed. It also notes the cost per call. This is highly transparent, and with no annotations, the full burden is on the description.

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 a bit longer than strictly necessary, with six sentences, but each sentence adds value: purpose, output, make-specific usage trigger, no-guess policy, output characteristics, and cost. It is well-structured and not rambling.

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?

The description covers the purpose, the conditions for use, the output nature (reworded definition, source, licence), the no-guess policy, the make-specific distinction, and the cost. Without an output schema, this is sufficient for an agent to understand what the tool returns and how to invoke it.

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 input schema already provides complete descriptions for both 'code' and 'make', including the distinction between generic and make-specific meanings. The tool description reinforces this but does not add substantive new information beyond the schema, so it stays at the baseline.

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 clearly states the tool looks up vehicle fault codes (OBD-II DTCs), which is specific and distinct from sibling tools like recalls or VIN decoding. The verb 'look up' and the resource are unambiguous.

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 explicitly says 'Use this when a scan tool reported a code,' providing a clear trigger. It also gives guidance on passing 'make' for manufacturer-specific definitions. However, it does not explicitly mention alternatives (e.g., when to use vehicle_recalls instead), so it falls short of the highest bar.

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