WASImancer: A WebAssembly-Powered MCP StreamableHTTP Server

WASImancer is an innovative Model Context Protocol (MCP) server built with Node.js that enhances tool execution through WebAssembly plugins. Leveraging the Extism framework, it enables seamless integration of WebAssembly modules as plugin functions, creating a flexible and powerful environment for model interactions.

What makes WASImancer special is its ability to load and execute tools as WebAssembly plugin functions, providing:

• Fast, near-native performance for tool execution
• Language-agnostic plugin development through WebAssembly
• Secure sandboxed execution environment
• Seamless integration with the Model Context Protocol
• Easy extensibility through the Extism plugin framework

Think of WASImancer as a bridge between the MCP ecosystem and the vast possibilities of WebAssembly, allowing developers to write plugins in their preferred language while maintaining high performance and security.

Authentication and Admin tokens

WASImancer needs two tokens, and you can set these two tokens with environment variables:

1. A bearer authentication token to protect the SSE endpoints (the communications between the MCP Client and the MCP Server), use WASIMANCER_AUTHENTICATION_TOKEN=mcp-is-the-way (if you want to disable the authentication, set it to NO_AUTHENTICATION).

   ⚠️ Important: The authentication token is used to protect the endpoints. If you don't set it, anyone can connect to your server and send commands. This is a security risk, so make sure to set it in production.

2. A bearer admin token to protect the prompts, ressources and tools management endpoints (eg: uploading a new tool, removing a resource...), use WASIMANCER_ADMIN_TOKEN=wasimancer-rocks

✋ If you don't set these tokens, the server will generate them for you at evry start (Look at the logs). You can use them to test the server, but you should set your own tokens for production.

Start WASImancer

node index.js

Or:

docker compose --file compose.dev.yml up --build

You can use the Inspector project to test WASImancer

#npm install @modelcontextprotocol/sdk
npx @modelcontextprotocol/inspector

Start Docker distribution of WASImancer

docker run --rm -p 3001:3001 \
  -e HTTP_PORT=3001 \
  -e PLUGINS_PATH=./plugins \
  -e PLUGINS_DEFINITION_FILE=plugins.yml \
  -v "$(pwd)/plugins":/app/plugins \
  -e RESOURCES_PATH=./resources \
  -e RESOURCES_DEFINITION_FILE=resources.yml \
  -v "$(pwd)/resources":/app/resources \
  -e PROMPTS_PATH=./prompts \
  -e PROMPTS_DEFINITION_FILE=prompts.yml \
  -v "$(pwd)/prompts":/app/prompts \
  -e WASIMANCER_ADMIN_TOKEN=wasimancer-rocks \
  -e WASIMANCER_AUTHENTICATION_TOKEN=mcp-is-the-way \
  -e UPLOAD_PATH=./plugins/bucket \
  k33g/wasimancer:0.0.7 

Or with Docker Compose:

services:  
  wasimancer-server:
    image: k33g/wasimancer:0.0.7
    environment:
      - HTTP_PORT=3001
      - PLUGINS_PATH=./plugins
      - PLUGINS_DEFINITION_FILE=plugins.yml
      - RESOURCES_PATH=./resources
      - RESOURCES_DEFINITION_FILE=resources.yml
      - PROMPTS_PATH=./prompts
      - PROMPTS_DEFINITION_FILE=prompts.yml
      - WASIMANCER_ADMIN_TOKEN=wasimancer-rocks
      - WASIMANCER_AUTHENTICATION_TOKEN=mcp-is-the-way
      - UPLOAD_PATH=./plugins/bucket
    ports:
      - 3001:3001
    volumes:
      - ./resources:/app/resources
      - ./plugins:/app/plugins
      - ./prompts:/app/prompts

docker compose up