Agent rules
The rules every AI agent must follow when calling the WriteStack MCP server, including the manual Sync step, capacity checks and read-before-write.
These rules are also in the tool descriptions the server sends, so a well-behaved client already sees them. They are here in one place so you can check an agent's behaviour, or put them in a system prompt.
1. Scheduling over MCP does not reach Substack on its own
When a writer schedules inside WriteStack with the browser extension installed, the Note is synced to Substack right away. An MCP client can't do that: it only stores Notes in the writer's WriteStack queue. The writer then opens WriteStack, goes to My Notes → Scheduled notes, and clicks the yellow Sync N scheduled notes to Substack button so the extension pushes them to Substack. See Sync.
- Before calling
schedule_notesorschedule_notes_with_custom_dates, tell the writer this and ask them to confirm. - Pass
userConfirmedManualSync: trueonly after they say yes. Without it, the server refuses and asks you to confirm first. - After scheduling, remind them to click Sync.
2. Check capacity before scheduling
Call get_schedule_capacity first. Schedule at most remaining Notes unless unlimited is true. The rest stay as drafts or ready Notes. If the limit is reached, the server schedules nothing and says so.
3. Write in the writer's voice
Before drafting new Note text, call get_writing_style, unless the writer already pasted full style instructions. Note bodies are Markdown, and a line break is a blank line (two newlines).
4. Never invent ids or names
Read them from the matching list tool:
| Value | Get it from |
|---|---|
| Tag names | list_tags |
| Buffer channel ids | list_buffer_channels (max 20 per Note) |
Newsletter publicationId | list_article_newsletters, then ask the writer which one |
| Note ids | list_notes, get_queue |
| Article ids | list_articles |
5. Ask before optional extras
- Link previews: if a Note contains a link, ask before attaching a preview card. Pass
includePreviews: trueonly after a yes. One preview per Note, from the first link. - Cross-posting: ask before adding Buffer channels.
- Newsletter: never pick a default newsletter for an article.
6. Read before you write
update_note and update_article replace the fields you send, and there is no undo.
- Read the Note or article first, show the writer the change, then write.
- For articles, call
get_articleright beforeupdate_articleand pass itscontentVersionasbaseVersion. A version conflict means the writer edited it in the meantime: read it again. - Pushing an article that already has a Substack draft updates that draft. If the draft was changed on Substack since the last push, the push stops with a conflict instead of overwriting. Tell the writer and let them decide.
7. What the server cannot do
- Sync Notes to Substack (the writer clicks the Sync button in WriteStack).
- Unschedule Notes (the writer does that in WriteStack).
- Act on any account other than the signed-in writer's.
If the writer asks for something no tool covers, call get_feature_suggestion_link and give them the link to suggest it.
Copy into a system prompt
You are connected to the writer's WriteStack account over MCP.
- Scheduling only queues Notes in WriteStack. Before scheduling, tell the writer they must open WriteStack (My Notes → Scheduled notes) and click the yellow "Sync N scheduled notes to Substack" button afterwards, and only pass userConfirmedManualSync: true after they confirm.
- Call get_schedule_capacity before scheduling and never schedule more than `remaining` unless `unlimited` is true.
- Call get_writing_style before drafting Note text. Use blank lines between paragraphs.
- Never invent tag names, channel ids, note ids or publication ids; read them from the list tools.
- Ask before adding link previews, Buffer channels, or choosing a newsletter.
- Read a note or article before updating it; updates overwrite and cannot be undone.