executeJavaScript
Execute JavaScript code in a secure cloud sandbox
LABSCO SUMMARY
The file tools are what make this usable — execution alone gives you stdout, and stdout is not where most work lands.
Two of the five tools run code; three move files. That ratio is the right one, because a script that writes a CSV, renders a chart or transforms a dataset leaves its result on disk, and an executor without a read path can only tell you it finished. Upload, list and read close that loop. The trade to understand is where the trust boundary sits: the code runs in E2B's infrastructure under your key, so this is safer than running it locally and is not the same thing as running it nowhere.
What it is
A thin client over E2B's sandboxes with five tools: execute JavaScript, execute Python, and upload, list and read files inside the sandbox.
What you get
- executeJavaScript and executePython run code in a cloud sandbox rather than on the host the agent is running on.
- uploadFile puts a file into the sandbox so code has something to work against.
- listFiles and readFile let the agent see what the run produced, which is what turns a one-shot execution into something it can iterate on.
Requirements
E2B_API_KEY. The sandbox is E2B's, so quota and session lifetime follow their account, not this server.
Setup effort
One command plus a key — npx -y smart-e2b, then supply credentials
USE CASES
01
Running code you would not run on your own machine
Execute it in the sandbox instead of the host, so an unfamiliar script cannot reach your filesystem.
02
Working on a file rather than a snippet
Upload the input, run the script against it, then read back what it produced — the loop that stdout alone cannot close.
5 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
executePython
Execute Python code in a secure cloud sandbox
listFiles
List files in a directory in the sandbox
readFile
Read a file from the sandbox
uploadFile
Upload a file to the sandbox
BEFORE YOU INSTALL
What to know first
Tools you get
5 tools when we connected.
Requires
- npx on PATH
- Node.js
- E2B_API_KEY in your environment
Where it runs
The documented client runs the server on your machine.
CONTEXT COST
Light Standing cost
Rated by the size of the 5 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Server setup
TERMINAL
npx -y smart-e2bMCP Clients
Claude Desktop
CLAUDE DESKTOP · JSON
{
"mcpServers": {
"smart-e2b": {
"command": "npx",
"args": [
"-y",
"smart-e2b"
],
"env": {
"E2B_API_KEY": ""
}
}
}
}
