apple-mail-mcp

update_draft

DestructiveIdempotent

Update an existing email draft by replacing fields like recipients, subject, body, and attachments. Preserves threading headers while recreating the draft with a new ID.

Instructions

Update an existing draft. Implemented as delete-and-recreate.

Returns a NEW draft_id — Mail.app forbids mutating saved drafts, so update is implemented by reading the draft's current state, deleting it, and creating a new draft with the merged fields. Threading headers (for reply seeds) and forward anchor are preserved via persisted seed metadata.

Field merge semantics: any non-None argument overrides the existing value. None keeps the existing value. attachment_paths=None PRESERVES existing attachments (extracted via Mail's save command); [] explicitly clears them; a list replaces.

For drafts created externally (not via create_draft), seed recovery falls back to scanning Mail.app for the In-Reply-To header — this can be slow on large mailboxes (~30s+ per call). Forward seeds without disk state are misclassified as fresh; pass an explicit body if so.

Input Schema

TableJSON Schema

Name	Required	Description
`cc`	No
`to`	No
`bcc`	No
`body`	No	Override body. None keeps existing. Non-None replaces (including the empty string, which clears).
`subject`	No	Override subject. None keeps existing.
`draft_id`	Yes	Mail.app id of the existing draft.
`send_now`	No	``False`` (default) saves new draft. ``True`` sends after eliciting confirmation.
`body_html`	No	Optional HTML body for the recreated draft (see ``create_draft``). Requires IMAP credentials and is limited to drafts whose seed is a fresh draft (not reply/forward) and to ``send_now=False``. NOTE: because the draft is recreated and draft state captures only plain text, an existing HTML draft is NOT preserved across an update unless ``body_html`` is passed again. (#251)
`from_account`	No	Override sender.
`template_name`	No
`template_vars`	No
`attachment_paths`	No	Override attachments. None preserves existing via temp-dir extraction; [] clears; list replaces.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Tool Definition Quality

A4.5/5.0

Behavior5/5

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

Beyond annotations (destructiveHint=true, idempotentHint=true), the description fully discloses the delete-and-recreate implementation, new draft_id return, field merge semantics, and edge cases like external draft seed recovery slowness and HTML body preservation limits. No contradictions with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured, starting with core purpose, then implementation details, then merge semantics and edge cases. It is somewhat lengthy but every sentence provides valuable information, earning its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (delete-and-recreate, merge semantics, attachment handling, external draft issues), the description covers most critical aspects. It lacks explicit error handling or performance notes, but presence of output schema mitigates need for return value details.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds significant meaning beyond the input schema, especially for attachment_paths (None preserves, [] clears, list replaces) and body. It explains the general merge rule (non-None overrides). However, not all 12 parameters are individually detailed; some like cc/to/bcc rely on the general rule, leaving minor ambiguity.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states it updates an existing draft, explains the delete-and-recreate mechanism, and distinguishes from create_draft by noting it returns a new draft_id. The verb 'update' with resource 'existing draft' is specific and unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explains when to use this tool (to modify a draft) and provides context on Mail.app limitations. It gives guidance on attachment behavior and seed recovery for external drafts, but lacks explicit 'when not to use' or comparison to similar tools like delete_draft.

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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