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:

Path	Method	Description
/health	GET	Health check (no API key)
/ping	GET	Auth check — returns ok if API key header is present
/mcp	POST	MCP Streamable HTTP endpoint

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

Variable	Required	Default	Description
PORT	no	3000	HTTP listen port
ALLOWED_HOSTS	no	—	Comma-separated Host header allowlist (recommended in production)
SHORTPIXEL_API_URL	no	https://api.shortpixel.com/v2	Upstream SPIO API base URL
SHORTPIXEL_PLUGIN_VERSION	no	MCP01	Plugin version sent to SPIO
LOG_LEVEL	no	info	Log verbosity: debug, info, warn, error
LOG_FORMAT	no	text	text = human-readable lines; json = structured JSON
LOG_MCP_PROTOCOL	no	true	Log inbound/outbound MCP JSON-RPC payloads

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

Request logging

Logs go to stdout (pm2 logs / npm start).

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:

Event	When
http_request	Every request (method, path, status, duration, MCP method/tool)
spio_request	Outgoing call to SPIO reducer.php
spio_response	SPIO result summary (status, % improvement)
mcp_auth_missing	Request without API key

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.

pm2 logs shortpixel-mcp
# or
npm start

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

Deploy on dev server

cd /xxx/mcp.shortpixel.com
npm ci
npm run build
cp .env.example .env
# set ALLOWED_HOSTS and PORT, then run behind nginx with TLS
npm start

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

Tool	Description
optimize_image_urls	Optimize one or more public image URLs via SPIO reducer API

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

Kind	Style	Example
Files	kebab-case	spio-api-client.ts
Classes	PascalCase	SpioApiClient
Methods	camelCase	optimizeUrls

Scripts

Command	Description
npm run build	Compile TypeScript to dist/
npm start	Run HTTP MCP server
npm run dev	Run with tsx (no build step)