List mailboxes in the Fastmail account. By default returns all mailboxes with full metadata; on accounts with hundreds of mailboxes the full result can exceed the MCP tool result window. Use properties: ["id","name","parentId"] for a slim view, and/or parentId to filter to one level of children.

Look up a single mailbox by its full path from root (e.g. "Folder/Subfolder/Leaf"). Returns the mailbox ID and minimal metadata, or throws "Mailbox not found" if no exact match. The path separator is "/"; folder names containing a literal "/" are not supported.

Create a new mailbox (folder). Returns the new mailbox ID. The caller is responsible for validating the name is appropriate (length, character set, parent-folder allow-list) before calling — JMAP itself only enforces uniqueness within a parent.

List emails from a mailbox

Same as list_emails (lists emails from a mailbox, optionally filtered by mailboxId, with paging and sort) but returns ONLY metadata fields on each result — id, threadId, subject, from, to, replyTo, receivedAt, hasAttachment, keywords. Does NOT return preview or any body-derived content. Use in privacy-sensitive flows where the workflow needs only the envelope (e.g. customer-mail least-privilege scans, or any caller forbidden from ingesting message bodies). Pair with get_email_metadata for follow-up lookups that should also stay header-only.

Get a specific email by ID

Get headers/metadata for an email — sender, recipients, subject, date, threading, mailbox membership, keywords (read/flagged/etc.), size, and whether an attachment is present — but NOT the body, preview, or any rendered text. Useful when a workflow needs to classify or route an email without ingesting its content (e.g. customer-mail least-privilege flows where reading bodies is forbidden, or skills that only need to verify post-archive folder placement). The return shape is the standard JMAP Email object restricted to a strict header-only allowlist.

Send an email

Reply to an existing email with proper threading headers (In-Reply-To, References). Automatically fetches the original email to build the reply chain. By default sends immediately; set send=false to save as a draft instead.

Create an email draft without sending it. Supports threading headers for replies. IMPORTANT: each call creates a new draft — do not call twice for the same message.

Edit an existing draft email. Since JMAP emails are immutable, this atomically destroys the old draft and creates a new one with the updated fields. Only fields you provide will be changed; others are preserved from the original draft.

Send an existing draft email. The draft must have recipients (to/cc/bcc) and a from address. After sending, the email is moved to the Sent folder and the draft keyword is removed.

Full-text search of email body and subject. Does not filter by sender, recipient, or date — use advanced_search for field-specific filtering. Drafts are included by default; set excludeDrafts=true to omit draft messages from results.

Same as search_emails (free-text search across subject and body) but returns ONLY metadata on each match — id, threadId, subject, from, to, replyTo, receivedAt, hasAttachment, keywords. The query still searches body text on the server side; only the result envelopes come back, never preview or body excerpts. Use when a content match is required (e.g. "find all messages mentioning X") but the matches must not surface body fragments to the caller.

List contacts from the address book

Get a specific contact by ID

Search contacts by name or email

List all calendars

List events from a calendar

Get a specific calendar event by ID. Returns organizer and participants when available.

Create a new calendar event. Supports date-only (e.g. 2026-04-01) for all-day events. DTEND is exclusive per RFC 5545 — a one-day event on April 1 needs end: 2026-04-02.

Update an existing calendar event. Preserves all existing data (attendees, reminders, recurrence rules, etc.) not being changed. Omit a field to leave it unchanged; passing an empty/whitespace string for title, description, or location is rejected (use clearFields to delete description/location). Floating times preserve the original timezone; explicit UTC/offset times convert to UTC. WARNING: providing participants replaces ALL existing attendee data (acceptance status, roles, etc.). participants: [] removes all attendees.

Delete a calendar event by ID

List sending identities (email addresses that can be used for sending)

Get the most recent emails across all mailboxes except Trash and Spam (pass mailboxName to scope to one folder, e.g. "inbox")

Mark an email as read or unread

Pin or unpin an email

Delete an email (move to trash)

Move an email to a different mailbox

Archive an email — move it to the target mailbox AND mark it as read in a single atomic JMAP operation. Equivalent to calling move_email followed by mark_email_read, but in one MCP call and one Email/set patch (the move and the read flag land together or not at all). For trashing an email, use delete_email instead — that follows a different convention and does not auto-mark-read.

Add labels (mailboxes) to an email without removing existing ones

Remove specific labels (mailboxes) from an email

Get list of attachments for an email

Download an email attachment. If savePath is provided, saves the file to disk and returns the file path and size. Otherwise returns a download URL.

Advanced email search with multiple criteria. Mailbox scoping supports a single mailbox (mailboxId), an intersection of multiple mailboxes (requiredMailboxIds — must be a member of ALL listed mailboxes), and exclusion (excludeMailboxIds — member of NONE of the listed mailboxes), alongside the standard sender / recipient / subject / free-text / date / attachment / unread / pinned filters.

Same filter capabilities as advanced_search (single-mailbox scoping via mailboxId, multi-mailbox intersection via requiredMailboxIds, exclusion via excludeMailboxIds, plus sender / recipient / subject / free text / date / attachment / unread / pinned) but returns ONLY metadata on each match — id, threadId, subject, from, to, cc, replyTo, receivedAt, hasAttachment, keywords. Does NOT return preview or any body-derived content. Use in privacy-sensitive flows where the routing decision is made from headers alone — for example, when classifying customer mail by sender / recipient / subject / thread state without ingesting body content. The free-text query still searches body content on the server side; only the result envelope comes back without body excerpts.

Get all emails in a conversation thread. Draft messages are excluded by default; set includeDrafts=true to include in-progress drafts in the thread.

Same as get_thread (enumerate every message in a conversation thread) but returns ONLY metadata on each thread message — id, threadId, subject, from, to, cc, replyTo, receivedAt, hasAttachment, keywords. Does NOT return preview or any body-derived content. Use for thread-state checks (reply-presence detection, sender enumeration, date comparison, read/flagged status) without ingesting message bodies — particularly in customer-mail least-privilege flows where the skill needs to know "did we reply, when, and from which alias" but is forbidden from reading what was said. Accepts either a thread ID or an email ID and resolves to the parent thread, mirroring get_thread.

Get statistics for a mailbox (unread count, total emails, etc.)

Get overall account summary with statistics

Mark multiple emails as read/unread

Pin or unpin multiple emails

Move multiple emails to a mailbox

Delete multiple emails (move to trash)

Add labels to multiple emails simultaneously

Remove labels from multiple emails simultaneously

Check which MCP functions are available based on account permissions. Calendar tools run over CalDAV, so calendar is reported available when CalDAV credentials are configured, regardless of the JMAP calendar capability.

Test bulk operations by finding recent emails and performing safe operations (mark read/unread)