Create a new Substack draft post from Markdown.

Args: title: Post title (max 280 chars). content_markdown: Body in Markdown. Supports headings, bold/italic, links, bullet lists, blockquotes, code blocks, and images ( - local paths are auto-uploaded to Substack CDN). subtitle: Optional subtitle (max 280 chars). audience: Who can read it: 'everyone' (default), 'only_paid', 'founding', or 'only_free'.

Returns: Summary including post_id, title, edit_url.

Update an existing draft. Provide only the fields you want to change.

Args: post_id: Draft ID returned by create_draft or list_drafts. title: New title (optional). subtitle: New subtitle (optional). content_markdown: New body in Markdown (optional, replaces full body). audience: New audience setting (optional).

Returns: Updated draft summary.

Upload an image to Substack's CDN and return its public URL.

Args: image_path: Local file path (e.g., /Users/foo/cover.png) or remote URL.

Returns: {url, id, width, height} — pass url to set_cover_image or embed in Markdown as .

Set the cover (thumbnail) image for a draft.

The cover image is shown on the publication homepage, in social shares, and as the email header. Use upload_image first to get a CDN URL.

Args: post_id: Draft ID. image_url: Substack CDN URL from upload_image, or any public image URL.

Returns: Updated draft summary.

Publish a draft immediately.

Args: post_id: Draft ID. send_email: If True (default), send the post as an email to subscribers. If False, publish to web only without emailing. share_automatically: If True, auto-share to Substack social channels.

Returns: {post_id, title, public_url, post_date, send_email}

Schedule a draft to publish at a future datetime.

Args: post_id: Draft ID. iso_datetime: ISO 8601 datetime, e.g., '2026-05-15T09:00:00+09:00' for JST or '2026-05-15T00:00:00Z' for UTC.

Returns: {post_id, scheduled_for}

Cancel a scheduled publish, keeping the post as a draft.

Args: post_id: Draft ID.

Returns: {post_id}

List recent drafts (unpublished posts).

Args: limit: Max number of drafts to return (1-50). Default 10.

Returns: List of draft summaries with post_id, title, edit_url, etc.

Get full details of a specific draft, including the body content.

Args: post_id: Draft ID.

Returns: Full draft data including draft_body (ProseMirror JSON).

Permanently delete a draft. This cannot be undone.

Args: post_id: Draft ID.

Returns: {post_id, deleted: true}

Post a Note (Substack's short-form, X/Threads-like post) to the public feed.

Notes are different from Posts:

• No title or subtitle.

• No email delivery to subscribers.

• Not added to the publication's article archive.

• Visible in the Substack Notes feed (cross-publication discovery surface).

Use Notes for:

• Quick thoughts, links, restacks, questions to your audience

• Daily presence between long-form posts

• Networking with other Substackers (replies, mutual follows)

Args: text: Plain text body. Use \n\n to separate paragraphs and \n for soft line breaks. Max 4000 chars (Substack's practical Notes limit).

Returns: {note_id, url, raw}