Replicate Streamable

Lightweight MCP server for AI image generation and editing using Replicate's official models.

Release status (2026-07-27): this repository pins @modelcontextprotocol/server and the test-only @modelcontextprotocol/client to 2.0.0-beta.5, with Zod 4 and the candidate 2026-07-28 protocol. The dated protocol and stable v2 SDK are not final at this commit; do not claim final conformance until the release gate is verified.

The Bun and Cloudflare Workers entry points share one fetch-native handler per deployment and create a fresh MCP server for every request. Modern HTTP is stateless; compatibility with 2025-era clients uses the SDK's stateless fallback and does not create MCP sessions.

Author: overment

Overview

This is a focused, minimal MCP server designed specifically for image generation workflows. Unlike full-featured Replicate MCP Servers, this server exposes only what's needed for image generation and editing with official models like Flux, SDXL, and Seedream.

Recommended usage: Tell your assistant upfront which model you prefer and any specific settings (quality, aspect ratio, style). This reduces tool calls and gets better results faster.

Example system prompt addition:

For image generation, use black-forest-labs/flux-schnell with 16:9 aspect ratio unless I specify otherwise.

Notice

This repo works in two ways:

• As a fetch-native Bun server for local workflows
• As a fetch-native Cloudflare Worker for remote interactions

Features

• Search Models — Find image generation models with full input schemas
• Generate Images — Run predictions and get results with expiring URLs
• Lightweight — Only 2 tools
• API Key Auth — Simple Bearer token or X-Api-Key header authentication
• Dual Runtime — Node.js/Bun or Cloudflare Workers

Design Principles

• LLM-friendly: Two focused tools, not 1:1 API mirrors
• Schema-aware: Search returns input schemas so agent knows exact parameters
• Secure: Replicate API key stored as secret, clients use separate bearer token
• Clear feedback: Model parameters, generation time, markdown-ready output

---

Installation

Prerequisites: Bun, Replicate Account.

Ways to Run (Pick One)

1. Local Development — Standard setup with bearer token auth
2. Cloudflare Worker (wrangler dev) — Local Worker testing
3. Cloudflare Worker (deploy) — Remote production

---

1. Local Development — Quick Start

1. Get Replicate API token:

   • Visit replicate.com/account/api-tokens
   • Create a new API token
   • Copy the token (starts with r8_)

2. Configure environment:

cd replicate-mcp
bun install
cp env.example .env

Edit .env:

PORT=3000

# Generate with: openssl rand -hex 32
API_KEY=your-random-auth-token

# Replicate API Token (from replicate.com)
REPLICATE_API_TOKEN=r8_your_token_here

3. Run:

bun dev
# MCP: http://127.0.0.1:3000/mcp

Claude Desktop / Cursor:

{
  "mcpServers": {
    "replicate": {
      "command": "npx",
      "args": ["mcp-remote", "http://localhost:3000/mcp", "--transport", "http-only"],
      "env": { "NO_PROXY": "127.0.0.1,localhost" }
    }
  }
}

---

2. Cloudflare Worker (Local Dev)

bun x wrangler dev --local | cat

Create .dev.vars for local secrets:

API_KEY=your_random_auth_token
REPLICATE_API_TOKEN=r8_your_replicate_token

Endpoint: http://127.0.0.1:8787/mcp

---

3. Cloudflare Worker (Deploy)

1. Update wrangler.jsonc for the production URL and exact Host/Origin allowlists. The checked-in values are local-safe defaults.

2. Set secrets:

# Generate a random token for client authentication
openssl rand -hex 32
bun x wrangler secret put API_KEY
# Paste the generated token when prompted

# Replicate API token
bun x wrangler secret put REPLICATE_API_TOKEN
# Paste your Replicate token when prompted

3. Validate generated types and deploy:

bun run types:worker
bun run types:worker:check
bun run build:worker
bun run deploy

Endpoint: https://<worker-name>.<account>.workers.dev/mcp

---

Client Configuration

Alice App

Add as MCP server with:

• URL: https://your-worker.workers.dev/mcp
• Type: streamable-http
• Header: Authorization: Bearer <your-API_KEY>

Claude Desktop / Cursor (Local Server)

{
  "mcpServers": {
    "replicate": {
      "command": "npx",
      "args": ["mcp-remote", "http://localhost:3000/mcp", "--transport", "http-only"],
      "env": { "NO_PROXY": "127.0.0.1,localhost" }
    }
  }
}

Claude Desktop / Cursor (Cloudflare Worker)

{
  "mcpServers": {
    "replicate": {
      "command": "npx",
      "args": ["mcp-remote", "https://your-worker.workers.dev/mcp", "--transport", "http-only"]
    }
  }
}

MCP Inspector (Quick Test)

bunx @modelcontextprotocol/inspector
# Connect to: http://localhost:3000/mcp (local) or https://your-worker.workers.dev/mcp (remote)

---

Tools

search_models

Search for models and get their input schemas. Returns up to 5 models with full parameter details.

// Input
{
  query: string;  // Model name, task, or keywords
}

// Output
### owner/name
Description of the model
Runs: 1,234,567

Input parameters:
  - prompt [REQUIRED]: string
  - aspect_ratio: enum: ["1:1", "16:9", "9:16"] = "1:1"
  - num_outputs: integer = 1
  ...

Example:

{ "query": "flux" }

generate_image

Run an image generation model and wait for the result.

// Input
{
  model: string;                    // "owner/name" format
  input: Record<string, unknown>;   // Model-specific parameters
}

// Output
## Image Generated in 2.3s

Model: black-forest-labs/flux-schnell

Display the image to the user using markdown syntax:

![Generated image](https://replicate.delivery/...)

Note: URLs expire in 1 hour.

Common input patterns:

// Text-to-image
{
  "model": "black-forest-labs/flux-schnell",
  "input": {
    "prompt": "a cat on the moon",
    "aspect_ratio": "16:9"
  }
}

// Image editing
{
  "model": "black-forest-labs/flux-kontext-pro",
  "input": {
    "prompt": "change the sky to sunset",
    "image": "https://example.com/source.jpg"
  }
}

---

Popular Models

Model	Speed	Best For
black-forest-labs/flux-schnell	~2s	Quick generations, drafts
black-forest-labs/flux-dev	~10s	Higher quality, detailed
bytedance/seedream-4	~5s	Versatile, multi-reference
black-forest-labs/flux-kontext-pro	~8s	Image editing with text

Aspect Ratio Guide

Ratio	Use Case
1:1	Portraits, icons, profile pictures
16:9	Landscapes, cinematic, desktop wallpapers
9:16	Mobile wallpapers, stories, vertical content
4:3	Classic photo format
21:9	Ultra-wide cinematic

---

HTTP Endpoints

Endpoint	Method	Purpose
/mcp	POST	MCP JSON-RPC 2.0
/health	GET	Health check

---

Environment Variables

Node.js (.env)

Variable	Required	Description
REPLICATE_API_TOKEN	✓	Replicate API token (r8_...)
API_KEY	✓	Auth token for MCP clients
PORT		Server port (default: 3000)
HOST		Server host (default: 127.0.0.1)

Cloudflare Workers (wrangler.jsonc + secrets)

Relevant wrangler.jsonc vars:

"vars": {
  "MCP_TITLE": "Replicate",
  "MCP_VERSION": "1.0.0"
}

Secrets (set via wrangler secret put):

• API_KEY — Random auth token for clients
• REPLICATE_API_TOKEN — Replicate API token

No KV namespace or MCP session store is required by the v2 serving shell.

---

Development

bun dev           # Start with hot reload
bun run typecheck # TypeScript check
bun run lint      # Lint code
bun run build     # Bun production build
bun run build:worker
bun run types:worker:check
bun test           # Modern, legacy, security, and provider-mock tests
bun start          # Run Bun production entry point

---

Architecture

src/
├── config/
│   └── metadata.ts              # Tool descriptions
├── tools/
│   ├── search-models.tool.ts    # Search with schema enrichment
│   └── generate-image.tool.ts   # Run predictions
├── services/
│   └── api/
│       └── replicate.service.ts # Replicate API client
├── http/
│   ├── app.ts                   # Fetch-native HTTP shell
│   ├── auth.ts                  # MCP API-key boundary
│   ├── body.ts                  # Bounded request bodies
│   └── security.ts              # Host, Origin, and strict CORS
├── core/
│   ├── mcp.ts                   # Fresh server factory
│   └── runtime.ts               # Deployment-scoped v2 handler
├── index.ts                     # Bun entry
└── worker.ts                    # Workers isolate entry

---

Troubleshooting

Issue	Solution
401 Unauthorized	Check API_KEY is set and client sends Authorization: Bearer <token>
"REPLICATE_API_TOKEN not configured"	Set secret: wrangler secret put REPLICATE_API_TOKEN
"Invalid model format"	Use owner/name format (e.g., black-forest-labs/flux-schnell)
"Missing required parameters"	Call search_models to see exact input schema
"Rate limit exceeded"	Wait a moment and retry
"Image URL expired"	URLs expire after 1 hour — generate again

Debugging

Test with MCP Inspector:

bunx @modelcontextprotocol/inspector
# Connect to your endpoint and test tools

Check Worker logs:

wrangler tail

---

License

MIT