List the mailboxes the user explicitly connected. New mailboxes are not included automatically.
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "list_mailboxes"
}
}| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds a meaningful behavioral detail: 'New mailboxes are not included automatically', which tells the agent that the result is a static snapshot of explicitly connected mailboxes and may become stale. This goes beyond what annotations provide.
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 short sentences with zero filler. The primary action is front-loaded ('List the mailboxes'), and the caveat about automatic inclusion is stated in the second sentence. 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 read-only list operation with no parameters and no output schema, the description is nearly complete. It states the scope and the important caveat about new mailboxes. The only minor gap is that it does not describe the return format (e.g., array of mailbox names or IDs), but for a list tool this is typically self-evident and the lack of an output schema reduces the expectation.
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 no parameters, and the schema is trivially 100% covered. With zero parameters, the baseline is 4. The description does not need to add parameter details, and it correctly focuses on the tool's behavior rather than nonexistent inputs.
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 clearly states the verb 'List' and the resource 'mailboxes', and specifies the scope: 'the user explicitly connected'. This distinguishes it from sibling tools like list_folders, which operate on folders, and search_messages, which searches content. The additional note about new mailboxes not being included automatically clarifies a non-obvious boundary.
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 implies when to use this tool (when you need the user's connected mailboxes) but does not explicitly mention alternatives or when not to use it. It doesn't reference sibling tools like list_folders or search_messages, leaving the agent to infer the appropriate context. This is adequate but not explicit.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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