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 goes well beyond these by explaining exactly how the credential is resolved, that exactly one authenticated request is made, what metrics are reported, and that the credential itself is never returned. This gives an agent a clear model of the tool's runtime behavior.

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: the first explains the mechanism, the second enumerates the reported outputs, and the third covers safety and usage. It is front-loaded, specific, and every sentence adds operational value.

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 diagnostic tool with no output schema, the description fully covers what an agent needs: behavior, return contents, safety (never returns credential), and when to call it. The sibling context and annotations cover the remaining operational constraints.

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, so the schema provides nothing to document and the baseline is 4. The description does not need to explain parameters; it instead explains what the no-input call returns, which is the relevant semantic content for this tool.

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 states a specific diagnostic verb ('healthcheck', 'resolves the credential ... makes one authenticated request') and clearly distinguishes this from the data-fetching sibling tools like vt_search_products and vt_get_product. It identifies the target resource (api.viator.com) and the exact outputs reported, leaving no ambiguity about what the tool does.

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 clearly positions it as a diagnostic fallback relative to the sibling tools. It does not name specific alternatives or state when not to use it, but the usage context is unambiguous.

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