Helio — Claude Code MCP server: what it does, how to install
A governance proxy sitting between agents and MCP tools. It enforces spending caps, requires prerequisite checks, and audits actions outside model context.
claude mcp add helio -- npx -y @gethelio/proxyWhat Helio does
Helio acts as a gateway intercepting tool execution requests before they reach your MCP servers. It validates every call against rules declared in helio.yaml, halting disallowed actions and capping expenses across external APIs. Because guardrails live inside the proxy rather than the model prompt, context window eviction or prompt injections cannot silence them.
Setup requires Node.js to run @gethelio/proxy via npx @gethelio/proxy init, creating the base configuration and a local dashboard. When deployed under the same OS user account as the agent, local processes can alter audit logs or restart the proxy. Running Helio inside an isolated container eliminates that risk.
What it helps with
- prevent unauthorized tool calls such as production database deletions
- cap daily spending across paid downstream APIs
- route actions exceeding financial thresholds for human approval
- log tool execution history tied to configuration file hashes
Example prompts for the agent
- Issue a refund of 80 pounds for order 402
- Purge inactive records from the production table
- Check customer details before running the account update
How to install Helio
Platform CLI
claude mcp add helio -- npx -y @gethelio/proxyPlatform CLI
codex mcp add proxy -- npx -y @gethelio/proxyConfig file
{
"mcpServers": {
"proxy": {
"command": "npx",
"args": [
"-y",
"@gethelio/proxy"
]
}
}
}Config file
{
"servers": {
"proxy": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@gethelio/proxy"
]
}
}
}Platform CLI
gemini mcp add proxy npx -y @gethelio/proxyStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Helio
How to install Helio in Claude Code?
Run claude mcp add helio -- npx -y @gethelio/proxy in your terminal. You can generate the starting helio.yaml file by running npx @gethelio/proxy init in the project root.
Why run an external proxy for agent tools?
Models lose system prompt constraints as conversations grow, and malicious instructions can bypass in-context guardrails. Helio keeps budgets, permissions, and session records outside the agent environment.
How does Helio ensure audit records cannot be altered?
Every log entry includes the cryptographic hash of active settings. To prevent local agent scripts from editing these audit logs, run the proxy inside a container or as an independent operating system user.
