Preloop MCP Server

Preloop MCP server exists for a simple reason — assistants are far more useful when they can act on Preloop directly instead of describing what you should do. Use Preloop to onboard existing agents with one command, and to deploy event-driven agentic automations with governed tools and budgets.

What you get

Preloop is a single open-source platform that covers the five jobs teams otherwise buy from four different vendors:

• Accidental deletions. — One wrong command and your production database is gone
• Leaked secrets. — API keys pushed to public repos before anyone notices
• Runaway costs. — Agents spinning up expensive cloud resources without limits
• Breaking changes. — Untested deployments to production at 3am

What the assistant can call

Once Preloop is connected, these are the calls the assistant has available:

• One — tap approvals** from your phone, watch, or desktop — for any onboarded agent's tool calls, including native Bash/Edit actions, not just MCP tools
• Per — tool justification** — require (or optionally request) the agent to explain why a tool is being called
• name — "deploy-approval"
• expression — "args.command.contains('deploy') && args.command.contains('production')"
• OpenAI — compatible** (/openai/v1/models, /openai/v1/chat/completions, /openai/v1/responses) and Anthropic-compatible (/anthropic/v1/messages) endpoints
• Allowed — model lists** per account, flow, API key, or managed agent
• Runtime — plugin dependent:** live OpenClaw and Hermes command delivery requires their native runtime plugin to honor preloop.control.control_ws_url, own
• Capability — What it does
• Upgrading — The installer detects the existing install and keeps its configuration (public URL, TLS setup, SMTP credentials, SECRET_KEY, database password)

Setting it up

Being a remote server, there is no local install. You register the endpoint with your client, authorise it once, and the tools appear.

Configuration and credentials

You will need 4 environment variables: PRELOOP_URL, SMTP_HOST, WEBAUTHN_RP_ID, SECRET_KEY. The server will not start without them, which is usually why the tools fail to appear on a first run. Keep credentials in your client's env block or a secrets manager rather than in a file you might commit.

Choosing this one

This sits in the AI and media services group, where several servers overlap in what they claim to do but differ sharply once you actually set them up. Preloop's toolset — One, Per, name and 6 more — is a fair guide to whether it matches your workflow. It is maintained by preloop; worth a glance at recent repository activity before you build anything load-bearing on it.

This entry was verified against Preloop's own documentation before publication; SyncDev keeps the directory reviewed rather than auto-generated.

Before you rely on it

• Your data travels to the provider's service, so the usual questions apply about what you send and what they retain.
• With 9 tools registered it takes up a noticeable share of the context window; turn it off in projects that never touch Preloop.
• Missing credentials fail quietly in some clients — if no tools show up, check the environment block first.
• MCP clients confirm each tool call by default. Leave that on until you have watched what the preloop mcp server does with a few real requests.