Verify credentials and upstream reachability

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

Annotations already declare readOnly, idempotent, and openWorld hints. The description adds valuable behavioral context: it mimics real credential resolution, performs exactly one authenticated request, reports the credential source, acceptance, round-trip time, and a distinction among failure modes, and guarantees that the credential itself is never returned. This goes well beyond the annotations.

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 three sentences with no filler. It front-loads the core behavior, then the output payload, then the usage trigger. Every sentence earns its place and the length is appropriate for the tool's simplicity.

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?

For a zero-parameter, read-only healthcheck tool with no output schema, the description is complete: it explains what the tool does, what it reports, when to use it, and a key privacy guarantee. An agent has enough context to select and invoke it correctly without additional documentation.

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 schema description coverage is 100%, so the schema already fully documents the input contract. Per the baseline rule for zero-parameter tools, a 4 is appropriate; the description doesn't need to explain parameters, and it doesn't misleadingly mention any.

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 begins with a specific action ('Resolves the credential... makes one authenticated request to Kia Connect') and clearly defines the tool's diagnostic purpose. It distinguishes itself from the sibling session/login/vehicle tools by focusing on reachability and credential validation rather than on performing operations.

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 an explicit trigger: 'Call this when a real tool fails and you want to know which hop broke.' This tells an agent exactly when to invoke it, though it does not name specific alternatives or state when not to use it. The context is still clear enough to route correctly.

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