Verify credentials and upstream reachability

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

The description adds beyond annotations by explicitly stating it is read-only and 'never returns the credential itself', a safety-critical behavior. It also discloses that it makes one authenticated request and reports round-trip time, which are behavioral details not captured by the annotations. This is valuable transparency.

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 logically structured into action, outputs, and usage, and the essential details are front-loaded. It is slightly verbose with the repetition of the hostname and the long enumeration of failure modes, but every sentence earns its place. It could be tightened but remains clear and readable.

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 is complete: it explains what the tool does, what it reports, the safety guarantee, and when to use it. It covers the key return values (credential source, acceptance, round-trip time, and error hint) in plain language, so an agent has everything needed to invoke it correctly.

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?

There are zero parameters, and the schema is an empty object, so there is nothing to document. The description correctly focuses on behavior rather than parameters, and the baseline for 0 params is 4. It adds no parameter-specific meaning because none exist.

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 action (resolves credentials and makes an authenticated request to a named host) and explicitly reports the diagnostic outputs. It also distinguishes itself from siblings by framing the tool as a failure-diagnosis tool ('Call this when a real tool fails and you want to know which hop broke'). This gives clear, unambiguous purpose.

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 provides a clear, explicit trigger: 'Call this when a real tool fails and you want to know which hop broke.' However, it does not name alternative tools or state when not to use it, so it lacks the full when-not/alternatives guidance. The context is clear enough for an agent to decide, but not exhaustive.

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