Verify credentials and upstream reachability

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint. The description adds valuable behavioral context: it explicitly states 'Read-only; never returns the credential itself' and describes the exact outputs (source, acceptance, round-trip time, and a plain-English hint distinguishing failure modes). It also mentions that it makes one authenticated request, which is a side effect not covered by annotations. No contradiction with 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 approximately 70 words and front-loads the core action ('Resolves the credential... makes one authenticated request') before listing outputs and usage. Every sentence adds value: the credential resolution, the request, the reported metrics, the read-only/never-returns-credential note, and the when-to-call guidance. There is no redundancy.

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 diagnostic tool with no output schema, the description adequately explains what it does, what it reports, and when to use it. It specifies the three failure categories and mentions round-trip time, giving the agent a clear expectation of the result. No critical information is missing.

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% (vacuously). The description does not need to explain parameters because there are none. The baseline for 0 params is 4, and no additional parameter semantics are required or provided.

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 clearly states the tool's purpose: resolving the credential as real tools do and making an authenticated request to test upstream reachability. It explicitly distinguishes this healthcheck from the sibling tools (messages, expenses, etc.) by naming it as a diagnostic that reports credential source, acceptance, and round-trip time. The verb 'resolves' and 'makes' are specific, and the resource is named.

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 provides explicit guidance on when to call: 'Call this when a real tool fails and you want to know which hop broke.' This gives a clear trigger condition and implies it's for troubleshooting, not routine use. It does not mention alternatives, but the context is sufficient because this tool is unique among siblings for diagnostics.

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