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

Annotations already provide readOnlyHint=true, so the tool is known to be safe. The description adds useful behavioral context beyond that: the existence of a read-only Courier Recommended set and that runs can use it without prior creation. It does not contradict the annotations and provides a small but meaningful behavioral detail.

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 only two sentences and each earns its place. The first sentence states the operation clearly; the second provides a useful default-set fact that helps the agent understand expected data. No filler or redundant phrasing exists.

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, read-only list operation with no output schema, the description is complete enough. It names the resource, indicates the tool lists saved sets, and highlights the special default set. An agent can invoke this tool without any additional ambiguity.

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?

There are zero parameters in the input schema, so parameter semantics are essentially moot. The baseline for a zero-parameter tool is 4; the description does not need to explain parameters and does not attempt to invent them. The context about the recommended set is tangential but not misleading.

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 and resource: 'List saved preview device sets.' It clearly distinguishes itself from sibling get_preview_device_set by indicating this is the collection/list operation, and it adds the meaningful detail about the Courier Recommended set so an agent knows what will appear in results.

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: every workspace has a read-only Courier Recommended set, and runs can use it without creating it first. This helps an agent understand the default state before listing. However, it does not explicitly mention when to use list_preview_device_sets instead of get_preview_device_set or other siblings, so it falls short of full alternative routing.

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