ShortPixel Image Optimizer

ShortPixel MCP Server

Public HTTP MCP server that exposes ShortPixel SPIO image optimization to AI agents (Cursor, Claude Desktop, VS Code, etc.).

Architecture

AI client (Cursor, Claude, …)
    │
    │  MCP over HTTPS (Streamable HTTP)
    ▼
https://mcp.shortpixel.com/mcp
    │
    │  user's API key in Authorization header
    ▼
ShortPixel SPIO API (api.shortpixel.com)

Each request carries the user's own ShortPixel API key. The MCP server does not store user keys — it forwards them to the public SPIO API.

Requirements

• Node.js 20+
• npm

Install (server)

npm ci
npm run build
cp .env.example .env

Edit .env for server settings (port, allowed hosts, upstream API URL). Do not put user API keys in server .env.

Run

npm start

Endpoints:

Quick test (curl)

Server up, no API key:

curl http://mcp.shortpixel.com:3000/health

API key present (simple check):

curl -i -H "Authorization: Bearer YOUR_API_KEY" http://mcp.shortpixel.com:3000/ping

Use http:// (not https://) on port 3000 unless TLS is configured on nginx.

MCP request (important: Streamable HTTP clients must accept both JSON and SSE):

curl -s -N -X POST http://mcp.shortpixel.com:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

Authentication

Send the user's ShortPixel API key on every MCP request:

Authorization: Bearer <shortpixel_api_key>

Alternative header:

X-ShortPixel-Api-Key: <shortpixel_api_key>

Users without a key can get one at shortpixel.com.

Cursor setup (end user)

{
  "mcpServers": {
    "shortpixel": {
      "url": "https://mcp.shortpixel.com/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_SHORTPIXEL_API_KEY"
      }
    }
  }
}

Replace the URL with your deployed host during development (e.g. http://localhost:3000/mcp).

Server environment variables

For internal ShortPixel development, set SHORTPIXEL_API_URL=https://devapi2.shortpixel.com/v2.

Request logging

Logs go to stdout, which the shortpixel-mcp systemd service redirects to /var/log/shortpixel/mcp.log (npm start shows them directly when running locally).

Default (LOG_FORMAT=text) — narrative flow you can follow:

[2026-06-30 15:01:53] [1/5] → CLIENT | HTTP POST /mcp | JSON-RPC request: "initialize" (client connects) | id: 0
           {
             "jsonrpc": "2.0",
             "method": "initialize",
             "id": 0,
             "params": { ... }
           }
[2026-06-30 15:01:53] [1/5] ← SERVER | HTTP POST /mcp 200 | JSON-RPC response: "initialize" (client connects)
[2026-06-30 15:01:53] [2/5] → CLIENT | HTTP POST /mcp | JSON-RPC request: "notifications/initialized" (session ready, no response body expected) | id: null
[2026-06-30 15:01:53] [2.5/5] → CLIENT | HTTP POST /mcp | JSON-RPC request: "tools/list" (client asks which tools exist) | id: 1
[2026-06-30 15:01:53] [2.5/5] ← SERVER | HTTP POST /mcp 200 | JSON-RPC response: "tools/list" (client asks which tools exist) | tools discovered: optimize_image_urls
[2026-06-30 15:02:18] [3/5] → CLIENT | HTTP POST /mcp | JSON-RPC request: "tools/call" (client runs a tool) | id: 2 | tool: "optimize_image_urls"
[2026-06-30 15:02:18] [4/5] MCP → SPIO API: POST reducer.php (args mapped to SPIO payload) | ...
[2026-06-30 15:02:35] [5/5] MCP ← SPIO API: Success | reduction: 27.41% | optimized: http://api.shortpixel.com/f/...-lossy.jpg | original: ...
[2026-06-30 15:02:35] [3/5] ← SERVER | HTTP POST /mcp 200 | JSON-RPC response: "tools/call" (client runs a tool) | tool: optimize_image_urls
           { "jsonrpc": "2.0", "id": 2, "result": { ... } }
[2026-06-30 15:02:35]     ✓ round-trip done (16.3s)

LOG_MCP_PROTOCOL=false keeps only high-level app logs and hides MCP payload dumps.

Structured (LOG_FORMAT=json) — one JSON object per line:

API keys are masked (****abcd). Full keys are never logged.

Note: The chat prompt never reaches this server. The LLM (inside the MCP client) turns user text into a structured tools/call; the server only sees JSON-RPC arguments and maps them to the SPIO API.

tail -f /var/log/shortpixel/mcp.log
# or, running locally
npm start

Set LOG_LEVEL=debug for tools/list and extra HTTP lines.

Deploy

Runs as the shortpixel-mcp systemd service (unit file at /etc/systemd/system/shortpixel-mcp.service), which runs node dist/index.js directly (no pm2) and reads env vars from .env in the project directory (EnvironmentFile=).

cd /web/mcp.shortpixel.com   # liveVPS; a separate host from the rest of the PHP stack
npm ci
npm run build
# edit .env directly on the server (not deployed - gitignored)
sudo systemctl restart shortpixel-mcp
sudo systemctl status shortpixel-mcp

Re-upload package.json and package-lock.json after each dependency change. If build still fails, run npm ci --include=dev (some servers set NODE_ENV=production which skips devDependencies).

Available MCP tools

optimize_image_urls arguments:

• urls (required): Public image URLs to optimize (max 100)
• lossy: Compression level (0 lossless, 1 lossy, 2 glossy)
• wait: Max wait seconds (0 to return immediately, 1-30 to wait)
• upscale: Upscale factor (0, 2, 3, 4)
• resize: Resize mode (0 none, 1 outer, 3 inner, 4 smart crop)
• resize_width, resize_height: Resize target dimensions in pixels
• cmyk2rgb: Convert CMYK to RGB (1 yes, 0 no)
• keep_exif: Keep EXIF metadata (1 keep, 0 remove)
• convertto: Conversion value (+webp, +avif, +webp|+avif, webp|avif, jpg, png, gif)
• bg_remove: Background removal (1, image URL, or #rrggbbxx)
• refresh: Force source refetch (1) or use cached optimized data (0)
• paramlist: Per-URL overrides array (must match urls length)
• returndatalist: Any array echoed back unchanged in response

Project layout

src/index.ts                    HTTP server entry point
src/http/auth.ts                API key extraction from requests
src/mcp/create-mcp-server.ts    Per-request MCP server factory
src/clients/spio-api-client.ts  ShortPixel SPIO HTTP client
src/tools/spio-tools.ts         MCP tools
src/http/request-log-middleware.ts HTTP request logging
src/logging/request-logger.ts    Structured JSON logger
src/logging/mcp-protocol-log.ts  MCP protocol payload capture/normalize

Naming conventions

Scripts