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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, covering the safety profile. The description adds the workspace scoping ('connected to the current workspace') and the intended use case, but does not describe return format or pagination behavior. With annotations present, this is acceptable but not rich.

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 two sentences with no fluff. The core action ('List all domains connected to the current workspace') is front-loaded, followed by a purposeful usage hint. Every word earns its place.

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 simple list tool with an output schema, annotations covering safety, and zero parameters, the description is fully adequate. It states the scope (current workspace) and the use case, which are the only missing behavioral details. Nothing an agent needs to call this tool correctly is omitted.

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 has zero parameters, so schema coverage is trivially 100%. Per the baseline for 0 params, a score of 4 is appropriate. The description adds no parameter semantics because none are needed; it correctly describes the list behavior without redundant parameter information.

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 all domains', and adds scope with 'connected to the current workspace'. It also hints at a use case (audit and choose), making it clearly distinct from sibling operations like domain_get or domain_create. The purpose 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 provides a clear context for when to use the tool: 'Use this to audit configured sender domains and choose one for follow-up actions.' It implies the tool is for listing and selection, but does not explicitly mention when not to use it or name alternatives. This gives clear usage context without exclusions.

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