Send an email in Markdown to allow-listed recipients, with optional base64 attachments and reply threading.
Send an email written in Markdown. Every recipient must be on the allow list. Attachments are base64.
| Name | Required | Description | Default |
|---|---|---|---|
| cc | No | ||
| to | Yes | Recipients; every address must be on allow_send_to | |
| bcc | No | ||
| subject | Yes | ||
| attachments | No | ||
| reply_to_id | No | id of a received message this replies to | |
| body_markdown | Yes | Message body in Markdown |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden. It usefully discloses the allow-list gate and the base64 attachment encoding, but says nothing about irreversibility of sending, error behavior for non-allowed addresses, rate limits, or whether a message can be recalled.
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 short, declarative sentences with zero filler; the core action and the two most failure-prone constraints (allow list, base64) are front-loaded in that order.
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 7-parameter mutation tool with no annotations and no output schema, the description covers only the allow-list rule and encoding format. Missing are send irreversibility, failure semantics, and any per-parameter nuance for cc/bcc/subject/reply_to_id.
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 coverage is 43%. The description reinforces allow-list scoping (which the schema documents only for 'to', so extending it to cc/bcc adds value) and repeats the Markdown/base64 details already in the schema. It adds nothing about subject length limits, reply_to_id behavior, or attachment size.
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 concrete verb+resource ('Send an email') plus two salient characteristics (Markdown body, base64 attachments). This clearly separates it from the read/mutation siblings like list_messages, read_message, and delete_message, though it never explicitly names an alternative or contrast set.
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?
Gives one hard precondition ('Every recipient must be on the allow list') which tells the agent when a call will succeed, but offers no when-to-use framing, no alternative tool naming, and no guidance on cc/bcc vs to. Usage is implied rather than taught.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.