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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), so the description's value is in disclosing the response contract: severity, derates yes/no, meaning, part, price range, and page URL. That is genuinely useful behavioral context beyond the annotations, though nothing is said about rate limits or result count limits.

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?

Front-loaded with the verb and library scope, then the return contract. The trailing Spanish sentence largely restates the English rather than adding information, but given the bilingual tool it is a minor cost.

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?

No output schema exists, so the description correctly compensates by naming the returned fields. What it omits is routing guidance: with a near-identical sibling (search_fault_code_library) and related lookup tools, the description does not give an agent enough to choose correctly.

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%, so both params are already documented. The description restates the query modes ('SPN/FMI, P-code or free text') matching the schema, and adds nothing about the lang switch beyond the schema enum. Baseline 3 applies.

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 (Search) and resource (DERATE's 56-code heavy-truck library) with matching modes (SPN/FMI, P-code, free text). However it never differentiates itself from the sibling search_fault_code_library, which appears to overlap heavily, so an agent cannot tell them apart from the description alone.

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, no prerequisites, no indication of when to prefer this over search_fault_code_library or list_fault_codes. The bilingual framing implies it is the entry point for es/en lookups, but that is left to inference.

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