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Substack automation · runs daily

Reply to unanswered Substack comments

Two days after a send, the comment section under the post has grown past what you remember reading. The bell mixes those comments with likes, Notes replies and new followers, so some readers never hear back.

Cotlet does it in your own Substack account with list_posts, list_comments and reply_to_comment, called by your AI agent, an n8n workflow or a script.

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Hosted · nothing to install or maintain

Official options

Can Substack do this on its own?

Substack has no public API to read or answer comments (checked 12 Oct 2026). Substack offers Reply Rules and reader reporting (Settings > Community > Enable reporting) to hide or remove bad comments, but nothing that finds the comments you have not answered yet.

By hand

How you do it in Substack today

  1. Turn on Likes and comments notifications in the publisher dashboard Settings to get an email and an Activity notification for each new comment.
  2. Open the bell icon on Substack; the Activity section lists likes, replies, mentions, restacks and new subscribers together, and it cannot be cleared.
  3. Open each recent post on the web and scroll its Comments tab, expanding threads to see whether you already replied.
  4. Click Reply under each comment that still needs an answer, and pin a good one through the three dots menu if you want it on top.
  5. The checking repeats post by post, and older posts keep collecting comments after the notifications have scrolled away.

With an agent

How to reply to unanswered Substack comments

Prompt 

Every evening, find comments on my last three Substack posts that I have not answered, draft a short reply to each in my voice, and show me the drafts before posting.
  1. 01

    Pick the posts to cover

    list_posts gives the recent published posts. The agent covers the window you name, for example the last three posts or the last 14 days, so an old essay that suddenly gets comments is not skipped forever.

  2. 02

    Keep only the threads waiting for you

    list_comments runs per post with unanswered_only. A thread where a co-author or another reader already answered the question is listed as answered by someone else, not drafted.

  3. 03

    Decide what deserves a reply

    Questions and thoughtful disagreement get a draft. One-word praise gets a short thanks or nothing, by your rule. Spam, abuse and comments hidden by Reply Rules get no reply; the agent lists them so you can remove or ban in Moderation.

  4. 04

    Draft in your voice, then ask

    The agent reads the post and your past replies to match tone and length, and never promises dates or discounts you have not stated. Each reply_to_comment call waits for your OK, so you can edit or drop a draft.

  5. 05

    Report what stayed open

    After posting, the agent lists comments it left for you on purpose, such as a refund request or a personal question that belongs in email.

What you get back

Example data 

Checked 3 posts, 41 comments, 9 waiting for you
Drafted 6 replies: Maya Chen (pricing question), Tom Ruiz (disagrees on point 2), 4 others
Skipped 2: one-word praise
Left for you: Ana Brooks asks for a refund on her annual plan
Hidden by Reply Rules, not answered: 1 spam comment on "The quiet launch"

Other ways to ask

  • Only answer comments from paid subscribers on this week's posts.
  • Every morning, list unanswered questions on all posts from the last 30 days, no drafts.
  • Reply to every comment under "The quiet launch" with a short thank-you, and skip the ones I already answered.

Before you automate it

What Substack allows, and what to know first

  • Substack sets who can comment per post: everyone, free or paid subscribers, paid subscribers only, founding members or no one. Free subscribers can never comment on a paid post.
  • Substack Reply Rules hide comments that break your stated standards without notifying you or the commenter; hidden comments sit behind a "Replies hidden" label and in the Hidden tab of Moderation.
  • Paid subscribers, accounts you follow and contributors are not filtered by Substack Reply Rules, unless you deleted their comments before.
  • A reply on Substack shows up in the commenter's Activity section, where Substack lists replies to comments people have made.
  • Restacks of a post can show on its web version in a separate Restacks tab next to Comments; those are Notes, not comments, and the publisher hides one with "hide note from post" in its three dots menu.

reply_to_comment asks for your OK by default. To run it daily without you, switch confirmation off for that tool in your dashboard.

Sources: Substack: How do I enable or disable comments on my posts? · Substack: What are Reply Rules? · Substack: What is the bell icon on Substack? · Substack: Can I moderate comments on my Substack posts? · Substack: How can I publish on Substack? (notifications)

REST

Call reply_to_comment from a script

curl 

curl https://cotlet.dev/api/v1/substack/reply_to_comment \
  -H "Authorization: Bearer $COTLET_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"comment_id":"c_90417","body":"Thank you, Maya. Pricing is the whole of part two, out on Thursday."}'

Example response 

{
  "comment_id": "c_90432",
  "parent_id": "c_90417",
  "created_at": "2026-10-11T10:07:00Z"
}

MCP: add https://cotlet.dev/mcp/v1 with the same key; the tool is substack_reply_to_comment. Example data.

Schedule it in n8n, Make, Zapier or cron

Tools

Substack tools this automation uses

Cotlet Substack tools used to reply to unanswered Substack comments
Tool Parameters
list_posts status, limit, cursor
list_comments post_id, unanswered_only
reply_to_comment comment_id, body
All 14 Substack tools with descriptions

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