Webhook that writes a blog, newsletter or social post

Webhook that writes a blog, newsletter or social post

An n8n workflow behind a web address. You send it a POST with a topic and the kind of text you want. Claude writes a full
blog post, a newsletter issue or three social posts, the workflow answers with the draft as JSON, and a short preview goes to
a Slack channel.

What is inside

• workflow.json: the workflow as n8n exports it, five nodes, none of them a sticky note. It holds no credential.
• README.md: these notes.

What we changed from the original copy

• Build Prompt read the request as $input.first().json. A Webhook node hands over the call as headers, params, query
  and body, so topic, type, language and tone were never found and every run wrote about the default topic. It now
  reads $input.first().json.body.
• The three JSON bodies (the Claude request, the Slack message and the answer) placed raw text between quotes. A prompt with a
  line break stops the request at Claude, and a draft with a line break or a quote breaks the other two. Each value now goes
  through JSON.stringify(...).slice(1, -1).
• The webhook ID is gone.
• Nothing else. The key, the Slack path and the model are the file's own.

Before you start

• An n8n instance, on n8n Cloud or your own server.
• An Anthropic API key, and a Slack incoming webhook (its address ends in a path after https://hooks.slack.com/services/).
• A way to set two environment variables on the n8n server, or a willingness to type the values into the nodes.

Set it up

1. In n8n, create a workflow, open its menu and choose Import from File. Pick workflow.json.
2. Give n8n the key and the Slack path. The file reads them as {{ $env.ANTHROPIC_API_KEY }} in the x-api-key header of
   Generate Content, and as {{ $env.SLACK_WEBHOOK_PATH }} in the address of Notify via Slack. Set both as environment
   variables on the server, or replace each expression with the value itself.
3. Save, open Trigger Webhook and copy its test address. Send a POST with a JSON body (the examples are below).
4. When the draft looks right, publish the workflow and use its production address.

A test call:

{
  "topic": "Five ways to cut meeting time",
  "type": "newsletter",
  "language": "English",
  "tone": "friendly"
}

type is blog, newsletter or social. Without a topic the workflow writes about "AI automation trends", in
blog form, in English, with a professional but approachable tone.

How a run goes

1. Trigger Webhook (Webhook 2) takes the POST and waits for the answer to come from a Respond to Webhook node.
2. Build Prompt (Code) picks topic, type, language and tone from the body. It then chooses one of three prompts:
   a blog post of about 600 words, a newsletter issue of about 300 words, or three social posts for Twitter/X, LinkedIn and
   Instagram.
3. Generate Content posts the prompt to https://api.anthropic.com/v1/messages with claude-sonnet-4-6, up to 2,000 tokens
   and a system line that asks for useful, engaging writing.
4. Notify via Slack posts the topic, the type and the first 500 characters of the draft to your Slack webhook.
5. Return Content answers the caller with status, topic, contentType and content.

Change the look

• The three prompts: the prompts object in Build Prompt.
• The defaults: topic, contentType, language and tone at the top of the same node.
• The model and the length: model and max_tokens in Generate Content.
• The preview: the text in Notify via Slack. Delete the node to skip Slack.

Good to know

• Anthropic's deprecations page, read on 12 November 2026, lists claude-sonnet-4-6 as active, with a retirement date no
  sooner than 17 February 2027.
• Notify via Slack runs before Return Content, since it sits higher on the canvas. When the Slack address is wrong or
  empty the run stops there and the caller gets no draft. Delete the node, or fix the path, first.
• A type other than the three falls back to the blog prompt.
• The webhook has no authentication. Anyone who finds the address can start a run on your key, so turn on one of the Webhook
  node's authentication options before you share it.
• Each run is one Claude call of up to 2,000 tokens.
• The topic goes to Anthropic. Slack gets the topic and the start of the draft.