This tool builds a Substack `Post` from markdown content and posts a draft.
It supports optional tag assignment, prepublish (setup check), and publishing.

Args:
    title: Draft title.
    markdown: Markdown body content.
    subtitle: Optional subtitle text.
    audience: One of `everyone`, `only_paid`, `founding`, `only_free`.
    write_comment_permissions: One of `none`, `only_paid`, `everyone`.
    search_engine_title: Optional title for search engine optimization.
    search_engine_description: Optional description for search engine optimization.
    slug: Optional URL slug for the post.
    draft_section_id: Optional section ID for the draft.
    tags: Tag or list of tags to attach to the post.
    prepublish: If true, calls `prepublish_draft` after creation.
    publish: If true, calls `publish_draft` after creation (and optionally prepublish).
    send: Passed to `publish_draft` for newsletter delivery.
    share_automatically: Passed to `publish_draft`.

Returns:
    dict containing drafted post (`draft`), optional `tags`, `prepublish`, `publish` results.

Examples:
    With the YAML structure from the README, a caller can map fields like:

    ```yaml
    title: "My Post Title"
    subtitle: "My Post Subtitle"
    audience: "everyone"
    write_comment_permissions: "everyone"
    markdown: |
      # Hello

      This is the body.

    tags:
      - python
      - substack
    prepublish: true
    publish: true
    send: false
    share_automatically: true
    ```

    Then invoke via MCP directly:

    ```python
    from substack_mcp.mcp_server import post_draft_from_markdown

    result = await post_draft_from_markdown(
        title='My Post Title',
        markdown='# Hello

    A longer process with manual prepublish/publish calls:

    ```python
    from substack_mcp.mcp_server import (
        post_draft_from_markdown,
        prepublish_draft,
        publish_draft,
        add_tags,
    )

    d = await post_draft_from_markdown(
        title='Long flow',
        markdown='Content',
        tags=['a','b'],
        publish=False,
    )
    draft_id = d['draft']['id']

    await add_tags(draft_id, ['post-tag', 'news'])
    await prepublish_draft(draft_id)
    await publish_draft(draft_id, send=True, share_automatically=True)
    ```

    This docstring example is meant to mirror the YAML-driven workflow and show how to decompose the same operations into explicit tool calls.