@cryptoapis-io/mcp-simulate
MCP server for Crypto APIs Simulate product. Dry-run Ethereum transactions to preview results without broadcasting.
API Version: Compatible with Crypto APIs version 2024-12-12
Features
- Simulate Ethereum transactions before broadcasting
- Preview transaction results, gas usage, and state changes
- Ethereum only (mainnet, sepolia) — the underlying API endpoint has no blockchain parameter
Prerequisites
Installation
npm install @cryptoapis-io/mcp-simulate
Or install all Crypto APIs MCP servers: npm install @cryptoapis-io/mcp
Usage
npx @cryptoapis-io/mcp-simulate --api-key YOUR_API_KEY
export CRYPTOAPIS_API_KEY=YOUR_API_KEY
npx @cryptoapis-io/mcp-simulate
npx @cryptoapis-io/mcp-simulate --transport http --port 3000 --api-key YOUR_API_KEY
Claude Desktop
Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):
{
"mcpServers": {
"cryptoapis-simulate": {
"command": "npx",
"args": ["-y", "@cryptoapis-io/mcp-simulate"],
"env": {
"CRYPTOAPIS_API_KEY": "your_api_key_here"
}
}
}
}
Cursor
Add to .cursor/mcp.json (project) or ~/.cursor/mcp.json (global):
{
"mcpServers": {
"cryptoapis-simulate": {
"command": "npx",
"args": ["-y", "@cryptoapis-io/mcp-simulate"],
"env": {
"CRYPTOAPIS_API_KEY": "your_api_key_here"
}
}
}
}
MCP Inspector
npx @modelcontextprotocol/inspector npx @cryptoapis-io/mcp-simulate --api-key YOUR_API_KEY
n8n
- Start the server in HTTP mode:
npx @cryptoapis-io/mcp-simulate --transport http --port 3000 --api-key YOUR_API_KEY
- In your n8n workflow, add an AI Agent node
- Under Tools, add an MCP Client Tool and set the URL to
http://localhost:3000/mcp
n8n in Docker: localhost inside the container is not your machine. Start the server with --host 0.0.0.0 and MCP_AUTH_TOKEN set (see Exposing the server beyond localhost), use http://host.docker.internal:3000/mcp as the URL, and add an Authorization: Bearer <token> header to the MCP Client Tool credential.
All servers default to port 3000. Use --port to assign different ports when running multiple servers.
simulate_evm
Simulate an Ethereum transaction (dry run). Ethereum only — the underlying endpoint has no blockchain parameter.
| Parameter | Description |
|---|
network | Network: mainnet or sepolia |
fromAddress | Sender address |
toAddress | Recipient address |
value | Amount to send (in native coin) |
data | Contract call data (hex) |
gasLimit | Gas limit |
gasPrice | Gas price |
CLI Arguments
| Argument | Description | Default |
|---|
--api-key | Crypto APIs API key | CRYPTOAPIS_API_KEY env var |
--transport | Transport type: stdio or http | stdio |
--host | HTTP host (use 0.0.0.0 to accept remote connections — requires an auth token with --api-key) | 127.0.0.1 |
--auth-token | Bearer token callers must send (Authorization: Bearer <token>); prefer the MCP_AUTH_TOKEN env var | MCP_AUTH_TOKEN env var |
--allowed-hosts | Comma-separated Host header allowlist for non-loopback binds | — |
--port | HTTP port | 3000 |
--path | HTTP path | /mcp |
--stateless | Enable stateless HTTP mode | false |
HTTP API Key Modes
When using HTTP transport, the server supports two API key modes:
- With
--api-key: The key is used for all requests. x-api-key request headers are ignored.
- Without
--api-key: Each request must include an x-api-key header with a valid Crypto APIs key. This enables hosting a public server where each user provides their own key.
npx @cryptoapis-io/mcp-simulate --transport http --port 3000
Exposing the server beyond localhost
HTTP mode listens on 127.0.0.1 by default, so only processes on the same machine can reach it.
To accept connections from other machines or containers, bind explicitly and protect the port:
export MCP_AUTH_TOKEN=$(openssl rand -hex 32)
npx @cryptoapis-io/mcp-simulate --transport http --host 0.0.0.0 --port 3000 --api-key YOUR_API_KEY \
--allowed-hosts mcp.internal.example
npx @cryptoapis-io/mcp-simulate --transport http --host 0.0.0.0 --port 3000
--allowed-hosts restricts the Host header (DNS rebinding protection) when not bound to loopback. Prefer MCP_AUTH_TOKEN over --auth-token: command-line arguments are visible in the process list.
Stdio transport always requires an API key at startup.
Important: API Key Required
Warning: Making requests without a valid API key — or with an incorrect one — may result in your IP being banned from the Crypto APIs ecosystem. Always ensure a valid API key is configured before starting any server.
Remote MCP Server
Crypto APIs provides an official remote MCP server with all tools available via HTTP Streamable transport at https://ai.cryptoapis.io/mcp. Pass your API key via the x-api-key header — no installation required.
License
MIT