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

Annotations already declare readOnly, idempotent and closed-world, so the safety profile is covered. The description adds genuine behavioral context by enumerating what the response contains (severity, probable causes, tests with expected values, repair steps, cost estimate), which substitutes well for the absent output schema. It stops short of stating auth, rate limits, or unknown-code behavior.

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; the verb+resource leads and the response contract follows. The trailing list is long but each item is informative rather than redundant.

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 enumerates the returned fields, and read-only behavior is covered by annotations. The one meaningful gap is routing guidance against the many similar siblings, which leaves the agent guessing between this and interpret_derate or get_truck_fault_code.

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 both the 'query' and 'lang' parameters are already fully documented in the schema with examples and an enum. The description adds no format or syntax detail beyond what the schema provides, making the baseline 3 appropriate.

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 (explain) and resource (truck fault code or symptom) and scopes the response to DERATE terms. However, it does not distinguish itself from close siblings such as get_truck_fault_code, interpret_derate, or get_diagnosis, so an agent cannot tell them apart without opening the schemas.

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 gives no when-to-use or when-not-to-use guidance and never names alternatives, despite a crowded sibling set that includes list_fault_codes, search_fault_code_library, get_truck_fault_code and interpret_derate. Usage is only inferable from the verb 'explain'.

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