Verify credentials and upstream reachability

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

Annotations already indicate readOnlyHint, idempotentHint, and openWorldHint. The description adds meaningful behavioral detail beyond these: resolution mirrors real tool behavior, exactly one authenticated request is made, and it reports credential source, acceptance, round-trip time, and categorized failure hints. It also explicitly states it never returns the credential.

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 dense but every sentence serves a purpose: mechanism, reported outputs, usage trigger, and safety guarantee. It is front-loaded with the core behavior and does not waste words on restating the title.

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 fully explains what will happen, what is reported, how to interpret the plain-English hint, and the safety boundary. No critical operational detail 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 100% schema coverage, so the description has no parameter burden. The baseline of 4 applies because there is nothing to add; the description correctly avoids inventing parameter details.

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 names specific actions: resolves credentials, makes one authenticated request to api.viator.com, and reports specific diagnostics. It is clearly distinguishable from sibling tools like vt_search_products or vt_get_product, which are data-retrieval tools, whereas this is a healthcheck/diagnostic tool.

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 explicitly states when to call it: 'when a real tool fails and you want to know which hop broke.' It also implies a non-use by noting it never returns the credential itself, but it does not enumerate exclusions or alternative tools. Context is clear, though exclusions are minimal.

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