Mailbox MCP

Update a saved draft

update_draft

Destructive

Rewrite a draft that is already in the Drafts folder, in place of deleting it and saving a new one. Use this whenever the user wants a draft changed - a different wording, another recipient, a corrected subject. It replaces the whole message, so pass the FULL new version of every field, not just the parts that changed: anything you leave out is gone from the draft. Threading headers and the files already attached are carried over for you, so a draft made by draft_reply stays part of its conversation and its attachments survive the edit. THE UID CHANGES: the draft you get back is a new message and the old uid stops working, so use the uid in the result for any further edit. Nothing is sent and nothing reaches anybody.

Input Schema

TableJSON Schema

Name	Required	Description
`cc`	No	Cc addresses, in full - these REPLACE the draft's current ones.
`to`	Yes	Recipient email addresses, in full - these REPLACE the draft's current ones.
`uid`	Yes	The UID of the draft to update, from list_emails on the Drafts folder or from the result of the tool that created it. It must be a draft; ordinary mail filed in Drafts is refused rather than replaced.
`from`	No	Send as one of the other addresses on this mailbox instead of its default. Use it only when the user names an address to send from. It must be one already added to the mailbox; anything else is refused with the list of addresses that would have worked. The mail server still decides whether it will carry the address, and may refuse it at send time.
`html`	No	Optional HTML body. Send real markup, used exactly as given and never escaped or unescaped by us: `<p>Hi</p>`, never `<p>Hi</p>`. Escaped markup is delivered as visible tags and nothing will warn you. Leave it out unless you have real markup to send: the message still goes out as HTML, built from `text`, carrying the mailbox owner's HTML signature.
`text`	Yes	The new plain text body, in full. It replaces the draft's current body.
`subject`	Yes	The new subject, in full.
`attachments`	No	Files to attach. FOUR WAYS IN, AND ONLY ONE OF THEM COSTS YOU ANYTHING. For a file already in this mailbox, call read_email on the message holding it and pass the `ref` from its `attachments` list as `fileRef`. For a file on the web, pass its https:// link as `url` and this server fetches it. For a file on the person's own computer, make a link with create_upload_link and pass its `uploadId` once the file is up - one entry attaches everything that arrived there. Those three work at any size, because the bytes never pass through this conversation. `content` is the last resort and is only for something you generated yourself in this conversation that exists nowhere else: it costs roughly 450,000 tokens per megabyte, so keep it under about 50 KB. All attachments TOGETHER must come to under 10 MB - a whole-message limit, not an allowance per file, so three 4 MB files are refused however they arrived.
`plainTextOnly`	No	Send with no HTML part at all. Leave this out unless the user has asked for plain text or the recipient is a list that rejects HTML - it drops the mailbox owner's HTML signature and their formatting. Do not set it to be cautious; HTML is the normal format and what their own mail client sends.
`keepAttachments`	No	Keep the files already attached to the draft. Defaults to true, which is what editing a draft does in any mail client. Pass false ONLY when the user wants the existing attachments taken off; anything you pass in `attachments` is added either way.
`requestReadReceipt`	No	Ask the recipient's mail program to confirm when the message is opened, exactly as Outlook's "request a read receipt" tick box does. Only set it when the user asks for it. TELL THEM WHAT IT REALLY DOES before promising anything: it is a request their mail program may ignore and that many clients ask them to approve, so most messages never produce one however promptly they are read - consumer Gmail never sends one, Workspace only if an administrator enabled it, Apple Mail only behind a setting that ships off. Use check_receipts afterwards to see whether one came back, and never treat silence there as evidence the message was unread. There is no delivery-receipt option: that needs an SMTP feature none of the mail providers this connects to offer.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

First observedSep 5, 2026

TDQS

A4.8/5.0

Behavior5/5

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

The description goes well beyond the annotations. It discloses that the UID changes after editing, that old UIDs stop working, that threading headers/attachments are preserved, that nothing is sent, and that incomplete fields are removed from the draft. These are exactly the behavioral traits an agent needs to know before calling a destructive update operation.

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 dense but front-loaded: it states the action, the usage trigger, the replacement semantics, the side effects, and the safety guarantee in a tight sequence. A few capitalized reminders inside the schema carry the bulk of the maintenance, keeping the main description readable.

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

Completeness5/5

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

Although there is no output schema, the description tells the agent everything critical: what is replaced, what survives, what changes (UID), and what does not happen (nothing sent). Given the 11-parameter schema with rich per-parameter docs and the required fields, nothing essential for a correct invocation is missing.

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?

Schema coverage is 100%, so the schema already documents every parameter. The description still adds high-value semantic warnings: 'anything you leave out is gone from the draft', the UID-change consequence, and carried-over attachments. It doesn't need to restate the schema, but it clarifies the whole-message replacement semantics that the schema alone does not emphasize.

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 opens with a specific verb ('Rewrite a draft that is already in the Drafts folder') and immediately distinguishes the operation from deleting and re-saving. It clearly names the resource (a saved draft) and lists concrete triggers (different wording, another recipient, corrected subject), so an agent can identify it accurately.

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

Usage Guidelines5/5

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

The description explicitly says 'Use this whenever the user wants a draft changed', frames the mutation as in-place replacement, and gives practical warnings about passing the full new version of every field. It also names sibling alternatives like draft_reply implicitly through 'a draft made by draft_reply' and explains what carries over, giving clear context for when to edit vs recreate.

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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TDQS

A4/5.0

Disambiguation4/5

Most tools target clearly distinct actions, but there are several close pairs that require careful reading: check_bounces vs check_receipts, list_emails vs search_emails, and the send/reply/forward vs draft_email/draft_reply/draft_forward families. The descriptions are strong enough that a careful agent can disambiguate, but the boundaries are not always obvious from the tool names alone.

Naming Consistency5/5

Every tool uses a consistent snake_case verb_noun convention, such as check_bounces, list_mailboxes, send_email, and update_draft. Related operations use parallel forms like mark_read/mark_unread and flag_email/unflag_email, making the naming predictable and coherent.

Tool Count2/5

With 28 tools, this exceeds the 25+ threshold where a tool set starts to feel too heavy. Email is a broad domain and many tools are individually justified, but the surface could be consolidated, especially the draft_forward/draft_reply/draft_email and send_email/reply_email/forward_email variants.

Completeness4/5

The core email lifecycle is thoroughly covered: send, read, search, move, delete, drafts, replies, forwards, folders, flags, attachments, upload links, contacts, identities, deliverability, bounces, and receipts. The main gap is that permanent deletion is referenced as a separate operation but no such tool is actually provided, and contact/identity management is effectively read-only.

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