list_images

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

With no annotations, the description carries the full burden of behavioral disclosure. It implies a read-only list operation but gives no detail on whether images are region-scoped, whether public/private images are included, or if there are any side effects. This is minimal and under-informative.

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 with no wasted words. It states the core action and resource compactly, which is appropriate for a simple list operation.

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 list tool with an output schema, the description is nearly sufficient. However, the presence of sibling list_regions raises ambiguity about whether the listing is region-scoped or global, and 'available' is not clarified. This is a moderate gap in an otherwise simple 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 takes zero parameters, which the schema already reflects. The description adds nothing about parameters because none exist, so the baseline of 4 for 0-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 'List available machine images' uses a specific verb and resource, clearly identifying its purpose. It is intuitively different from sibling tools like list_regions or list_instances, though it doesn't explicitly distinguish itself or clarify what 'available' means in context.

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?

There is no guidance on when to use this tool versus alternatives. The description implies you use it to see available machine images, but offers no prerequisites, exclusions, or scenario-based direction, leaving the agent to infer usage.

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