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

Annotations already declare readOnlyHint, and the description confirms this is a list operation. It adds useful behavioral context by describing the device fields returned (pvd_ id, display name, filterable attributes), going beyond the bare annotation.

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 tight and front-loaded. It states the purpose first, summarizes the entity shape, and closes with actionable usage guidance, with no wasted words.

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 tool without an output schema, the description is nearly complete. It tells the agent what the tool returns and how to use it. It could be slightly clearer about the filtering mechanism since no query parameters exist in the schema, but this is a minor gap.

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 no parameters, so schema coverage is effectively 100%. The description compensates by explaining what values will be present in the returned data, especially the pvd_ id and filter fields, which helps an agent understand how to use the output.

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?

Description states a specific verb and resource: 'List the email clients a preview can render on.' It clearly identifies this as a device enumeration tool and distinguishes it from device-set related siblings like list_preview_device_sets.

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 explicit downstream guidance: 'Use these ids in a device set or in create_preview_run.' It does not explicitly state when not to use this tool or compare it with sibling alternatives, but the usage context is clear.

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