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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, covering the safety profile. The description adds genuine behavioral context beyond that: the return contents (likely cause, urgency, immediate action, matching public fault-code pages) and the scope limit that guided diagnosis lives elsewhere.

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?

Two sentences, front-loaded with the action and input, followed by a scope/output sentence. Efficient and mostly waste-free, though the app-positioning clause 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 usefully covers what is returned, and the schema fully covers inputs while annotations cover safety. The only residual gap is explicit sibling routing between this tool and the code-based diagnostic tools.

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 coverage is 100%, so the four parameters are already documented, making 3 the baseline. The description goes slightly beyond by embedding a concrete symptom example ('DEF light on and truck limited to 55 mph'), which communicates the expected free-text granularity for the required symptom field.

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?

States a specific verb and resource ('Explain a diesel truck engine derate or power-loss symptom') and names the inputs and outputs precisely. It also separates itself from the sibling diagnostic tools by positioning this as 'the free public interpretation' versus the full guided diagnosis in the DERATE app.

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?

Gives a clear usage context: use this for a symptom described in plain language, as the free public interpretation, while tests and a work order belong in the DERATE app. It stops short of explicitly routing away from named siblings such as explain_fault_code or get_diagnosis when a code is already known.

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