list_instances

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

With no annotations, the description carries the burden of behavioral disclosure. It mentions the key behavior that omitting region lists across all regions, which is important. However, it does not mention pagination, rate limits, or other potential behavioral traits. For a simple read-only list tool, this is adequate but not exceptionally transparent.

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 extremely concise: two short sentences that directly state the tool's purpose and the key parameter behavior. Every word earns its place, and it is front-loaded with the action and resource.

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?

Given the tool's simplicity (one optional parameter), the presence of an output schema, and the lack of annotations, the description covers the essential usage and behavior. It could mention error handling or pagination, but for most use cases, the description is complete enough to guide an agent.

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 schema provides no description for the 'region' parameter (0% coverage), so the description compensates by explaining its semantics: if no region is specified, all regions are included. This adds meaning beyond the bare schema definition and helps the agent understand how to use the parameter.

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 clearly states the action ('List all Amazon Connect instances') and the resource ('Amazon Connect instances'), distinguishing it from siblings like describe_instance, create_instance, and delete_instance. The purpose is unambiguous and specific.

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 provides clear context on when to use this tool: it lists all instances, with the region parameter controlling scope. It implies that this is the broad-listing tool compared to describe_instance for single instances, although it doesn't explicitly name alternatives. The region behavior guidance is useful and sufficient.

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