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

The '[read]' marker merely restates the readOnlyHint/destructiveHint=false annotations rather than adding new behavioral context. It does convey scope ('connected' zones only, of the merchant), but says nothing about result volume, ordering, or what happens when no zones are connected.

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 sentence with no filler, front-loaded with the read marker and the resource, with the actionable next step trailing. Nothing to cut.

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 discovery tool with no output schema, the description covers what it returns and how the return value is used downstream. It stops short of describing the shape of the response (fields besides email_zone_id), which would be the last missing piece.

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 takes zero parameters, so there is nothing to mis-specify; baseline is 4. The description usefully names the key output field (email_zone_id) and where it is consumed, which partially substitutes for the absent output schema.

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?

States a specific verb+resource: lists connected e-mail zones (mail domains) of the merchant. The parenthetical clarifies what a 'zone' is, and the follow-on usage distinguishes it from the message-listing sibling.

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?

Explicitly tells the agent what to do with the result — pass email_zone_id to list_email_messages — which establishes this as the discovery step before message listing. It does not, however, address when to pick this over list_email_accounts or list_email_lists, which an agent could plausibly confuse.

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