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

Annotations already declare readOnlyHint, idempotentHint, and closed-world (openWorldHint=false); the description reinforces the closed-world scope ('library only') and adds a genuinely useful behavioral detail: unrecognized codes return 'unknown' rather than erroring. It does not describe latency, rate limits, or response fields beyond the verdict, so it stops short of full disclosure.

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 tight sentences, front-loaded with the verdict and its possible values; every clause carries signal. The Spanish half is a translation that adds little for an agent, a minor redundancy in an otherwise lean definition.

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 compensates by naming the full verdict domain (stop / service_soon / info) plus the 'unknown' case, and annotations cover the safety profile. For a two-parameter read tool this is close to complete; only the broader response shape (e.g., accompanying message or code echo) is left unstated.

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%: the 'code' parameter documents accepted formats ('SPN 3251 FMI 0', '3251/0', 'P20EE') and 'lang' documents its enum and default. The description adds no parameter-level meaning, so the 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+resource (returns a safe-to-drive verdict for a truck fault code) and enumerates the output domain (stop / service_soon / info). It scopes itself with 'from DERATE's library only' and notes the 'unknown' fallback, which implicitly separates it from library-lookup siblings, though no sibling is named directly.

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?

Usage is implied rather than stated: an agent can infer this is the tool for a safety verdict on a code, and the 'DERATE's library only' + 'unknown' behavior sets a boundary. There is no explicit when-to-use guidance or routing to alternatives such as explain_fault_code, get_diagnosis, or interpret_derate.

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