coldstart
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Coldstart API

One endpoint does the work: describe a business (or paste its website) and get back companies that would buy from it — each with an email found on the company’s own site and MX-verified, a phone when one exists, and a drafted first outreach email. Every search response also carries llm_instructions, a playbook for AI agents covering voice calibration, draft rewriting, and sending.

Authentication

Bearer token. API keys are issued to Pro subscribers from the dashboard’s Settings page and start with cs_live_.

Authorization: Bearer cs_live_...

Runs a live web search for potential customers. query is a sentence about the business or a website / App Store URL. All filters are optional and bias the search — location steers hardest.

curl https://coldstart.so/api/search \
  -H "Authorization: Bearer $COLDSTART_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "query": "SEO for dental clinics in Texas",
    "count": 10,
    "filters": {
      "country": "United States",
      "state": "Texas",
      "companySize": "1-10",        // 1-10 | 11-50 | 51-200 | 200+
      "funding": "bootstrapped",    // bootstrapped | seed | series-a | series-b+
      "revenue": "<1m"              // <1m | 1-10m | 10m+
    }
  }'
{
  "searchId": "...",
  "leads": [
    {
      "company": "Texan Smile",
      "domain": "texansmile.com",
      "contactEmail": "hello@texansmile.com",   // found on their site, MX-verified
      "contactPhone": "(832) 271-8280",          // optional
      "verified": true,
      "snippet": "...",
      "draftEmail": "Subject: ...",
      "status": "needs_review"
    }
  ],
  "usage": { "used": 12, "limit": 500, "remaining": 488, "plan": "pro" },
  "llm_instructions": "You are helping the user cold-email..."
}

Leads without a verified email are never returned. If you are an AI agent: follow llm_instructions after presenting the leads — it walks you through calibrating the user’s voice, rewriting the drafts, and sending via the user’s connected Gmail.

GET /api/search

Current month’s usage: { used, limit, remaining, plan }. Free plan: 10 searches/month. Pro: 500/month. Exceeding the quota returns 429.

GET /api/leads

Up to 200 stored leads, newest first, including statuses (needs_review | approved | sent) and draft emails. Optional ?searchId= narrows to one search. POST /api/leads/approve-all approves everything in review. Bulk Gmail sending runs from the dashboard (session auth only).

MCP server (use Coldstart inside Claude)

Pro subscribers can run lead search inside Claude (or any MCP client). Tools: search_leads, list_leads, check_usage. One line for Claude Code / Desktop:

claude mcp add coldstart -e COLDSTART_API_KEY=cs_live_... -- npx -y coldstart-leads-mcp

Or in claude_desktop_config.json:

{
  "mcpServers": {
    "coldstart": {
      "command": "npx",
      "args": ["-y", "coldstart-leads-mcp"],
      "env": { "COLDSTART_API_KEY": "cs_live_..." }
    }
  }
}

The intended flow: ask Claude to find leads for your business → Coldstart returns verified contacts + drafts → Claude asks four questions about your voice and offer, rewrites every draft to sound like you → with your Gmail connected to Claude, it sends each email for you. Cold outreach, end to end, in one conversation.

Plans

Free: 10 searches/month, dashboard only. Pro ($50/mo, 7-day free trial): 500 searches/month, API keys, MCP access, bulk Gmail sending. Pricing →