Verify credentials and upstream reachability

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

Beyond the readOnlyHint and idempotentHint annotations, the description adds what a caller should expect: one authenticated request, the source of the credential, acceptance status, round-trip time, and a plain-English failure category. It also explicitly says the credential itself is never returned, which is important safety information not present in 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?

Every sentence earns its place: how the check works, what it reports, when to call it, and the read-only/no-credential warning. The description is compact, front-loads the mechanism, and avoids redundant restatement of 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 tool with no parameters and no output schema, the description still conveys the main reported outputs and the single side effect of one authenticated request. An agent can decide whether to call it and what to expect without needing additional structured metadata.

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 already documents an empty object, so there is nothing for the description to add about parameter meaning. The baseline for a parameterless tool applies.

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 uses a specific verb and resource: it resolves the credential the way real tools do, makes one authenticated request to api.getyourguide.com, and reports whether the credential was accepted. This clearly distinguishes the diagnostic healthcheck from the data-retrieval siblings such as gyg_search_tours and gyg_get_tour.

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?

It gives an explicit trigger: 'Call this when a real tool fails and you want to know which hop broke.' It doesn't explicitly state when not to use it or name an alternative diagnostic tool, but the intended context is clear and well differentiated from normal tool operations.

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