Verify credentials and upstream reachability

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

Annotations already declare readOnly, idempotent, and openWorld hints. The description adds meaningful behavioral details: it never returns the credential, makes exactly one authenticated request, and reports a plain-English hint distinguishing 'no credential', 'credential rejected', and upstream problems. This goes well beyond what annotations convey.

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?

Four sentences with no filler: the core behavior is front-loaded, followed by reported outputs, the read-only safety note, and the usage instruction. Every sentence earns its place and the description remains compact.

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?

Despite having no parameters and no output schema, the description covers inputs, behavior, outputs, side effects, and invocation context. An agent has everything needed to decide when and how to call this tool.

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 empty schema properties, so schema coverage is trivially 100%. There are no parameter semantics to describe, and the baseline of 4 for no-parameter tools 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 states a specific diagnostic purpose: resolve the credential the way real tools do, then make one authenticated request to generativelanguage.googleapis.com and report source, acceptance, RTT, and failure hint. This clearly distinguishes it from all sibling tools that generate images, video, or music, manage files, or interact with models.

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 explicitly instructs to call this tool when a real tool fails and you want to know which hop broke, giving clear context for use. It doesn't name a specific alternative or say when not to use it, but the diagnostic positioning is unambiguous given the sibling list.

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