List mail accounts

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so 'changes nothing' largely restates the safety profile. The real added value is the enumeration of return contents: email, alias, labels/calendar enablement, default account, and drafts-only versus sending mode, which tells the agent what signals it can act on afterwards.

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?

Three sentences, each doing distinct work: purpose, when-to-call, and what comes back. The scoping information is front-loaded and there is no filler.

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?

With no output schema, the description carries the full burden of describing return values, and it does so field by field, including the operationally important drafts-only mode flag and default-account marker.

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, so the baseline is 4; the description correctly confirms 'takes no input', removing any doubt about whether an account filter is required. Nothing further is possible for an empty 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?

The description opens with a specific verb and resource ('List the Gmail accounts this server can use'), which is unmistakably distinct from siblings like list_labels or list_drafts that also list things.

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?

It gives an explicit call condition ('first when the user has not said which mailbox') and states the downstream purpose: obtaining the alias values to pass as 'account' to every other tool. That is a clear when-to-use plus a named relationship to all siblings.

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