Documentation

The body can be a plain text string or a JSON object — sulfur handles both. For JSON, the message or error field is used as the event summary that Claude reads. For plain text, the full string is used. All other JSON fields are stored and accessible via event_detail on the paid plan.

A 202 Accepted with a JSON body:

{
  "id": "01JT4K...",           // unique event ID
  "signature": "a3f9c2d1e4b5", // deduplication hash of this payload
  "received_at": 1746835200    // Unix timestamp (ms)
}

If the same error fires repeatedly, the signature stays the same — that's how Claude can say "47 occurrences" instead of listing every event individually.

Over-limit requests return 429 Too Many Requests. No overages — events are dropped, not billed.

Any HTTP client works. The simplest form is a plain curl with no headers — good for shell scripts, cron jobs, and one-off diagnostics. Use JSON when you want Claude to see structured fields.

curl — plain text (simplest)

curl -X POST https://sulfur.sh/e/$TOKEN/my-app \
  -d "DB connection failed after 3 retries"

curl — JSON body (structured)

curl -X POST https://sulfur.sh/e/$TOKEN/my-app \
  -H "Content-Type: application/json" \
  -H "X-Severity: error" \
  -d '{"message":"DB connection failed","latency_ms":5200,"host":"db-1"}'

PowerShell — plain string

Invoke-RestMethod -Uri "https://sulfur.sh/e/$env:SULFUR_TOKEN/my-job" `
  -Method POST -Body "Scheduled job failed: exit code 1"

PowerShell — JSON body

$body = @{ message = "Scheduled job failed"; exit_code = 1 } | ConvertTo-Json
Invoke-RestMethod -Uri "https://sulfur.sh/e/$env:SULFUR_TOKEN/my-job" `
  -Method POST -ContentType "application/json" -Body $body

Cloudflare Worker (fetch)

async function logToSulfur(env, severity, payload) {
  await fetch(`https://sulfur.sh/e/${env.SULFUR_TOKEN}/my-worker`, {
    method: 'POST',
    headers: {
      'content-type': 'application/json',
      'x-severity': severity,
    },
    body: JSON.stringify(payload),
  }).catch(() => {/* fire and forget */});
}

Python (Lambda / scripts)

import requests

requests.post(
    f"https://sulfur.sh/e/{os.environ['SULFUR_TOKEN']}/my-function",
    json={"message": "Task failed", "step": "validation", "exit_code": 1},
    headers={"X-Severity": "error"},
    timeout=5,
)
# or plain text — no headers needed:
requests.post(f"https://sulfur.sh/e/{os.environ['SULFUR_TOKEN']}/my-function",
    data="Task failed during validation")

GitHub Actions (bash step)

- name: Log deploy result
  if: failure()
  run: |
    curl -X POST https://sulfur.sh/e/${{ secrets.SULFUR_TOKEN }}/deploy \
      -H "Content-Type: application/json" \
      -d '{"message":"Deploy failed","ref":"${{ github.ref }}"}'

Claude Desktop — edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "sulfur": {
      "url": "https://mcp.sulfur.sh",
      "transport": "streamable-http",
      "headers": {
        "Authorization": "Bearer slf_mcp_YOUR_TOKEN_HERE"
      }
    }
  }
}

Cursor — add to .cursor/mcp.json in your project root:

{
  "mcpServers": {
    "sulfur": {
      "url": "https://mcp.sulfur.sh",
      "headers": { "Authorization": "Bearer slf_mcp_YOUR_TOKEN_HERE" }
    }
  }
}