MCP-JS
MCP server that exposes a V8 JavaScript runtime as a tool for AI agents. Sandboxed JS execution for one-off computation, parsing, and transformation. 43 GitHub stars and 45 commits on main in the last 30 days. 0BSD license.
“MCP server that exposes a V8 JavaScript runtime as a tool for AI agents. Sandboxed JS execution for one-off computation, parsing, and transformation. 43 stars and 45 commits on main in the last 30 days.”
INSTALL THIS SERVER
{
"mcpServers": {
"mcp-js": {
"command": "npx",
"args": [
"-y",
"mcp-js"
]
}
}
}
{
"mcpServers": {
"mcp-js": {
"command": "npx",
"args": [
"-y",
"mcp-js"
]
}
}
}
{
"mcpServers": {
"mcp-js": {
"command": "npx",
"args": [
"-y",
"mcp-js"
]
}
}
}
{
"mcpServers": {
"mcp-js": {
"command": "npx",
"args": [
"-y",
"mcp-js"
]
}
}
}
{
"mcpServers": {
"mcp-js": {
"command": "npx",
"args": [
"-y",
"mcp-js"
]
}
}
}
4 TOOLS AVAILABLE
OUR ASSESSMENT
- 45 commits on main in the last 30 days. Top-tier cadence.
- 0BSD license, the most permissive option available.
- V8-based sandbox runs JavaScript inside the MCP process.
- Sandbox-reset tool prevents state bleeding between agent invocations.
- No authentication required; ready immediately after install.
- Arbitrary code execution inside the agent loop; review the agent prompt path before mounting in production.
- 43 stars indicates early adoption.
- Community-maintained; no vendor support.
V8 sandbox isolates from the host process via the V8 isolate boundary. Operators decide which globals to expose. Treat the agent flow as having capability to compute anything expressible in JavaScript: regex DoS, infinite loops, and crypto-mining patterns are within scope. Prefer a CPU and memory budget on the host process for production agent flows.
Agents that need ad-hoc JS computation without leaving the agent loop; data transformation flows where a custom MCP is overkill; debugging agents that want to evaluate snippets against runtime state.
TECHNICAL DETAILS
ADOPTION METRICS
// Reading this43 stars on r33drichards/mcp-js. 45 commits on main in the last 30 days, top-tier cadence.
// Reading thisPairs with Chrome DevTools, Claude Code, OpenSpec, MCP Inspector for dev-tools developer infrastructure. V8 sandbox surface is unique.
SOURCES & VERIFICATION
We don't take any single directory's word for it. Before scoring, we cross-reference 3 public MCP sources, install the server ourselves against the clients we cover, and record when we last re-verified.
The same server, 3 different lenses. We reconcile these signals into our editorial score, which is why our number sometimes diverges from a directory-aggregate star count.
| Source | Their rating | Their star count | Their downloads | Last synced |
|---|---|---|---|---|
| AutomationSwitch This page | 4.2editorial | 43 | — | MAY 6, 2026 |
| PulseMCP | — unrated | unavailable | unavailable | MAY 6, 2026 |
| MCP.so | — unrated | unavailable | unavailable | MAY 6, 2026 |
| Glama | — unrated | unavailable | unavailable | MAY 6, 2026 |
// Counts are directory-reported; we don't adjust them. Discrepancies usually come from different snapshot times or star-caching.
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