Creates a local plain-text email draft and returns an immutable draft ID plus preview; it never sends, so users can review intended messages before delivery.
Prepare a plain-text outgoing email locally; never sends. Returns an immutable draft ID and preview. Use only for the user's requested message. No attachments, Bcc or arbitrary From addresses.
| Name | Required | Description | Default |
|---|---|---|---|
| cc | No | ||
| to | Yes | ||
| body | Yes | ||
| subject | Yes |
Changes observed during successful MCP inspections.
v0.1.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false, which alone would leave an agent unsure how much state is mutated; the description resolves this by saying the draft is created 'locally' and is 'never' sent, and it adds that the draft ID is immutable and a preview is returned. It also discloses capability limits (no attachments/Bcc/From) not present in any structured field.
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?
Two compact clauses that front-load the action, immediately follow with the critical 'never sends' guarantee, then the return value and limits. Every clause carries distinct information with 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?
For a 4-parameter tool with no output schema, the description covers the essentials: side effects, return values (draft ID + preview), and capability exclusions. The remaining gap is per-parameter meaning, which is scored separately and is the only thing an agent would still have to guess.
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% and the description never explains what 'to', 'cc', 'subject', or 'body' accept — e.g. whether 'to' takes one address or many, or what the cc null default means. The only parameter-adjacent information is indirect: 'plain-text' constrains body format and 'No Bcc' implies a cc field exists.
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 and resource ('Prepare a plain-text outgoing email locally') plus the scope boundary ('never sends'), which immediately separates it from send_prepared_email and local_draft_status. An agent can distinguish this from all five siblings without opening a schema.
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?
'Use only for the user's requested message' gives a clear positive-usage constraint, and 'No attachments, Bcc or arbitrary From addresses' fences off invalid requests. It stops short of naming the follow-up tools (send_prepared_email, local_draft_status) or stating when to reuse a draft versus prepare a new one, so it is strong but not exhaustive.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.