Verify credentials and upstream reachability

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

Annotations already provide readOnly, idempotent, and openWorld hints, but the description adds meaningful behavioral detail beyond those: it states that exactly one authenticated request is made, that the credential itself is never returned, and that the output classifies failure modes ('no credential' vs 'credential rejected' vs 'Kia Connect-side problem'). This gives agents a clear safety and side-effect profile not available from the annotations alone.

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 ~100 words, front-loads the core action, then reports the output, then the read-only/security note, and ends with the usage trigger. Every sentence carries distinct information; no filler or repetition.

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 detailing what the tool reports (credential source, acceptance, RTT, hint) and what it never returns. Combined with the input-free schema and annotations, an agent has all necessary information to invoke this tool correctly and interpret its result.

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 tool has zero parameters and the schema coverage is 100%, so there are no parameter semantics to explain. The baseline of 4 applies, and the description accurately avoids inventing any parameter-related content.

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 opens with a specific verb and resource ('Resolves the credential... makes one authenticated request to Kia Connect') and enumerates the exact outputs (credential source, acceptance, RTT, plain-English hint). It also positions itself against siblings via 'Call this when a real tool fails' and its read-only diagnostic nature, clearly distinguishing it from vehicle command, auth-flow, and session tools.

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 a clear trigger condition: 'Call this when a real tool fails and you want to know which hop broke.' This is strong when-to-use guidance. It does not explicitly name alternatives or state when-not-to-use, but the diagnostic purpose is unambiguous in context with the sibling list.

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