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

With no annotations provided, the description must carry the behavioral disclosure burden. It signals a non-mutating read-only operation via 'Check whether' and discloses the behavioral dimensions it covers: reachability, serving state, and quota. It does not detail error behavior or response format, but it clearly states what the tool observes without contradicting any 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?

The description is a single, front-loaded sentence that immediately states the core action ('Check whether an instance is reachable and serving') and then appends the additional checks (status and quota state). There is no filler, repetition, or extraneous detail; every word contributes to the tool's purpose.

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 low-complexity tool with one fully documented parameter, the description sufficiently covers what the tool does and what it reports on: reachability, serving status, and quota state. There is no output schema to lean on, and the description could mention return format or error behavior, but for a simple health-check tool the provided information is largely complete.

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 input schema has 100% description coverage and already documents the single 'id' parameter as the instance/agent id returned by create_instance or list_instances. The tool description adds no additional parameter-level meaning, so the baseline score of 3 is appropriate because the schema does all the necessary explanatory work.

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 ('Check') with a clear resource ('an instance') and enumerates the exact aspects being checked: reachability, serving status, and quota state. This distinguishes it from sibling tools like create_instance, delete_instance, and pause_instance, which are clearly lifecycle mutations rather than health checks.

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 clear context for when to use the tool: whenever you need to assess whether an instance is reachable, serving, and within quota. It does not explicitly name alternative tools or state when not to use it, but the purpose is specific enough that an agent can infer the appropriate usage context.

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