list_instances

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

No annotations are present, so the description carries the burden of behavioral disclosure. It does convey that this is a read-only listing and narrows scope to running instances, but it does not mention pagination, ordering, rate limits, or whether instances across all regions are returned. Functional but incomplete.

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?

A single, front-loaded sentence states exactly what the tool does with no filler. Every word earns its place, and the scope is presented before anything else.

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 operation with an output schema and clearly differentiated siblings, the description is largely sufficient. It could be improved with explicit usage guidance and behavior notes, but an agent can correctly select and invoke the tool from the current description.

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 zero parameters, so there are no parameter semantics to document. The description's 'running instances' scope is the only relevant filter and is clearly stated.

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 verb and resource: 'List your running instances.' The 'running' qualifier and 'instances' resource clearly differentiate it from siblings like list_images, list_regions, and get_instance. It is unambiguous.

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 no explicit when-to-use guidance and names no alternatives. It implies 'use when you want running instances,' but it does not explain how to choose between this and get_instance or other list tools. Context must be inferred entirely from the tool name and sibling names.

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