API Reference Business

Generate professional writing with Claude via HTTP. Requires a Business plan API key.

Quick start

1. Subscribe to the Business plan and sign in.
2. Open Account → API keys → Generate API key.
3. Copy the key immediately — it is only shown once.
4. Send requests with Authorization: Bearer sn_...

Base URL

https://your-domain.com

Locally: http://localhost:3000

Authentication

Include your API key in every request:

Authorization: Bearer sn_your_api_key_here

• Keys start with sn_
• Up to 3 active keys per account
• Revoke keys anytime from your Account page
• Never expose keys in client-side browser code

Endpoints

Request headers

Request body (JSON)

{
  "prompt": "Write a cover letter for Alex Johnson applying for Senior PM at Acme Corp...",
  "toolId": "cover-letter",
  "toolName": "Cover letter",
  "tone": "professional"
}

Response — streaming (SSE)

Returns text/event-stream in Anthropic-compatible SSE format. Parse data: lines as JSON events. Text arrives in content_block_delta events:

data: {"type":"content_block_delta","delta":{"type":"text_delta","text":"Hello"}}

data: {"type":"message_stop"}

Response headers

Examples

cURL

curl -N -X POST https://your-domain.com/api/v1/generate \
  -H "Authorization: Bearer sn_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"prompt":"Write a professional cold email to a SaaS founder about partnership opportunities.","tone":"confident"}'

Node.js

const res = await fetch('https://your-domain.com/api/v1/generate', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer sn_YOUR_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    prompt: 'Write a LinkedIn bio for a fintech founder...',
    toolId: 'linkedin-bio',
    tone: 'professional',
  }),
});

const reader = res.body.getReader();
const decoder = new TextDecoder();
let output = '';

while (true) {
  const { done, value } = await reader.read();
  if (done) break;
  for (const line of decoder.decode(value).split('\n')) {
    if (!line.startsWith('data: ')) continue;
    try {
      const event = JSON.parse(line.slice(6));
      if (event.type === 'content_block_delta' && event.delta?.text) {
        output += event.delta.text;
        process.stdout.write(event.delta.text);
      }
    } catch {}
  }
}

Python

import requests, json

url = "https://your-domain.com/api/v1/generate"
headers = {
    "Authorization": "Bearer sn_YOUR_KEY",
    "Content-Type": "application/json",
}
payload = {"prompt": "Write ad copy for a fitness app...", "tone": "persuasive"}

with requests.post(url, headers=headers, json=payload, stream=True) as r:
    r.raise_for_status()
    for line in r.iter_lines():
        if not line or not line.startswith(b"data: "):
            continue
        data = line[6:].decode()
        try:
            event = json.loads(data)
            if event.get("type") == "content_block_delta":
                print(event["delta"].get("text", ""), end="", flush=True)
        except json.JSONDecodeError:
            pass

Error codes

JSON error shape:

{"error": "Invalid or missing API key. Use Authorization: Bearer sn_..."}

Limits

Manage keys

Generate and revoke keys from the web app: Account → API keys. Team members on a Business account inherit Business features but only the account owner can manage billing; API keys are tied to the user who creates them.

Support

Business customers get priority support: hello@sparknous.com