Queue outbound emails for a mailbox, applying recipient allowlist and consent checks to prevent unauthorized sends.
Queues an outbound email for a mailbox.
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | ||
| html | No | ||
| text | No | ||
| apiKey | No | ||
| subject | Yes | ||
| mailboxId | Yes |
Changes observed during successful MCP inspections.
v1.3.2Input schema / properties / apiKey / formatAdded value: +"starts_with"Input schema / properties / to / patternPrevious value: -"^(?!\\.)(?!.*\\.\\.)([A-Za-z0-9_'+\\-\\.]*)[A-Za-z0-9_+-]@([A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"New value: +"^(?:[A-Za-z0-9_'+\\-]+\\.)*[A-Za-z0-9_'+\\-]*[A-Za-z0-9_+-]@(?:[A-Za-z0-9][A-Za-z0-9\\-]*\\.)+[A-Za-z]{2,}$"v1.3.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure. 'Queues' usefully implies asynchronous enqueueing, but it does not mention authentication requirements, side effects, error conditions, or what happens after queueing.
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 extremely compact and front-loads the primary action with no wasted words. However, for a 6-parameter tool, this terseness comes at the cost of necessary operational context.
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?
This is a mutating operation with no annotations, no output schema, and six parameters, yet the description provides only a single clause. It omits required context such as how recipients are specified, how html/text relate, auth expectations, and what a caller should expect in response.
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?
Schema description coverage is 0%, so the description needed to compensate, but it adds no parameter-specific meaning. It gives only a vague mapping of 'mailbox' to mailboxId and leaves html/text, to, subject, and apiKey entirely to the 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 clearly names the action ('Queues') and the resource ('an outbound email') plus the target ('a mailbox'). It distinguishes the tool from most mailbox-read and mailbox-management siblings, though it does not explicitly disambiguate from assistantmail_send_email_reference.
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?
No guidance is given about when to use this tool versus alternatives such as assistantmail_send_email_reference or assistantmail_reply_message. Prerequisites, exclusions, and selection conditions are all absent.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.