Test Black Friday Subject Lines in Windsurf
Black Friday is won or lost in the inbox. With marginal connected to Windsurf, you can draft, test, and optimize Black Friday subject lines without leaving your editor — your AI agent handles the variants, the send, and the lift analysis.
Why run Black Friday subject line tests from Windsurf
Windsurf gives your AI agent direct access to the marginal email MCP server, so a single conversation can take a Black Friday campaign from idea to live subject line A/B test. Instead of bouncing between an ESP dashboard and your code, you describe the offer and let the agent generate and launch variants.
Black Friday inboxes are crowded, so small differences in framing — urgency, discount size, curiosity — produce measurable swings in open rate. Testing inside Windsurf keeps that iteration loop tight.
- Stay in one tool: prompt, test, and read results in Windsurf
- Move fast during the short Black Friday window
- Let your AI agent reason over open and click data, not just guess
- Reuse winning angles for Cyber Monday follow-ups
The marginal tools your agent will use
marginal exposes four MCP tools that map cleanly to a Black Friday subject line test. Windsurf calls them in sequence as you guide the campaign.
- generate_variants — spin up several Black Friday subject lines from one brief
- launch_test — start the subject line A/B test with a managed send
- get_results — pull open/click tracking and within-test lift metrics
- recommend_next — get a data-backed suggestion for the winning angle
A Black Friday workflow in Windsurf
Here is a typical flow once marginal is connected. You stay conversational; the AI agent handles the email marketing mechanics behind each step.
- Describe your Black Friday offer: discount, product, and audience
- Ask Windsurf to generate 4–5 subject line variants with different hooks
- Launch the subject line test as a managed send to your list
- Check get_results mid-flight for early open-rate signal
- Have the agent call recommend_next to lock in the winner
Getting connected
marginal is a hosted MCP server at https://marginal.sh/mcp, so there's nothing to deploy. Add the endpoint to Windsurf with your Bearer API key (marg_live_...) and your agent can immediately call the tools. The free tier covers 100 experiments per month — plenty to test multiple Black Friday subject lines and Cyber Monday variations.
Full setup steps and tool references live in the docs at https://marginal.sh/docs/.
- Endpoint: https://marginal.sh/mcp
- Registry: sh.marginal/mcp
- Auth: Bearer API key (marg_live_...)
- Free tier: 100 experiments/month
Get started with marginal
marginal is a hosted email marketing MCP server at marginal.sh. Sign up free, create an API key, and connect https://marginal.sh/mcp from Cursor, Codex, or Claude Desktop.
- 100 experiments/month on the free tier
- Four MCP tools: generate_variants, launch_test, get_results, recommend_next
- Listed in the MCP Registry as sh.marginal/mcp