n8n-guard

An MCP server for the operational layer underneath the n8n Public API.

Most n8n MCP servers on the registry wrap the same public endpoints: list workflows, list executions, create, activate, delete. That is useful for building workflows. It is close to useless for keeping a self-hosted instance alive, because the things that actually take an instance down are not in that API at all.

n8n-guard answers the four questions the API cannot:

1. How big is the datastore, and when does it become a problem? The Public API has no endpoint for database size. n8n-guard reads the SQLite file or queries Postgres directly, breaks the size down per table, derives the growth rate, and tells you how many days of headroom are left.

2. Which executions are stuck? Listing executions by status is not detection. A run sitting in running looks identical to a healthy long job until you compare it against what that workflow normally takes. n8n-guard builds a per-workflow median from finished runs and flags the outliers.

3. What is retention costing? How many execution records are stored, how far back they reach, and what a given retention window would free.

4. Has the instance drifted from git? Existing servers diff one API object against another. n8n-guard diffs the running instance against the JSON exports in a repository: live but never exported, exported but deleted, and content that quietly diverged.

It is strictly read-only. n8n-guard never writes to your instance, never deletes executions, and never activates or edits a workflow. It reports; you decide.

Install

npx -y n8n-guard

Requires Node.js 22 or newer (it uses the built-in node:sqlite). For a permanent install use npm install -g n8n-guard.

Claude Desktop / any MCP client

{
  "mcpServers": {
    "n8n-guard": {
      "command": "n8n-guard",
      "env": {
        "N8N_URL": "https://n8n.example.com",
        "N8N_API_KEY": "n8n_api_...",
        "N8N_SQLITE_PATH": "/var/lib/n8n/.n8n/database.sqlite",
        "N8N_GIT_REPO_PATH": "/srv/workflow-exports"
      }
    }
  }
}

Related MCP server: n8n-workflow-tester-safe

Configuration

Everything is an environment variable. There are no hardcoded hosts, paths, container names or accounts, so the server runs against any self-hosted instance.

Partial configuration is a supported mode, not an error. With only N8N_URL and N8N_SQLITE_PATH you still get disk and retention answers; the API-backed checks report that they are unconfigured and the rest of the run continues.

Tools

Example call

Point the server at an instance and let your client call a tool. Every tool answers with a readable summary first and the full structured payload after it:

## Retention report
- 200 execution records spanning 8.3 days (24.1/day)
- nothing older than 30 days, retention is already tight
- n8n-guard never deletes. To act on this, set EXECUTIONS_DATA_PRUNE=true and
  EXECUTIONS_DATA_MAX_AGE=720 (hours) on the n8n instance, then restart it.

followed by the structured payload the summary was derived from:

{
  "executionCount": 200,
  "oldestExecutionAt": "2026-08-28T23:43:28.651Z",
  "spanDays": 8.29,
  "executionsPerDay": 24.12,
  "buckets": [
    { "olderThanDays": 7, "rows": 32, "share": 0.16, "estimatedBytes": 3277 },
    { "olderThanDays": 30, "rows": 0, "share": 0, "estimatedBytes": 0 }
  ]
}

guard_run wraps all six checks. With only a datastore configured it reports the gap instead of aborting:

## Guard run (degraded)
- stuck_executions failed after 3 attempt(s): N8N_API_KEY is not set, so the n8n Public API cannot be queried
- git_drift failed after 2 attempt(s): N8N_GIT_REPO_PATH is not set, so there is nothing to diff the instance against
- 4 of 6 checks completed despite the failures above

Recovery: guard_run survives a partial outage

A monitoring run that aborts on the first unreachable dependency is worthless precisely when it matters. The API being down is the incident, and it is no reason to stop looking at the disk.

guard_run isolates every step. A failing step is retried with backoff, and if it still fails it becomes a finding while the remaining checks run to completion. Steps that depend on a failed step are skipped with the reason attached rather than crashing on missing input. The report says so plainly:

## Guard run (degraded)
- stuck_executions failed after 3 attempt(s): cannot reach http://n8n.internal:5678: fetch failed
- git_drift skipped: depends on instance, which failed
- 4 of 6 checks completed despite the failures above

This behaviour is covered by tests in test/unit/runner.test.ts and test/unit/serviceRecovery.test.ts, the latter running a real SQLite datastore against a deliberately dead API endpoint.

Render Workflows

The same sweep also runs as a Render Workflow: one Render task per check, with ordering, retries and backoff declared in the task definitions and executed by Render rather than by the in-process runner. Deploy steps, the task table and how to trigger a run (including a deliberate failure that demonstrates the retry path) are in docs/render-workflow.md.

Try it on a throwaway instance

The compose file starts a fresh n8n you can safely point the server at. The data directory is bind-mounted, which is exactly how n8n-guard reads a real deployment.

git clone https://github.com/flow-84/n8n-guard && cd n8n-guard
npm install && npm run build

docker compose up -d
./scripts/demo-setup.sh     # owner, API key, workflows, and a drifted export folder

The script generates the owner password, keeps it in the gitignored .n8n-demo-credentials, and prints it along with the environment block to run the server with. It seeds one workflow that matches its export, one that was never exported, one that points at a sink container so a run can hang, and one export whose workflow does not exist, so git_drift and stuck_executions have something real to find.

export N8N_URL=http://localhost:5679
export N8N_API_KEY=...            # printed by the script
export N8N_SQLITE_PATH=$PWD/.n8n-demo/database.sqlite
export N8N_GIT_REPO_PATH=$PWD/.n8n-demo-exports
npm start

The instance publishes on 5679, not on n8n's default 5678, so it cannot collide with an instance you care about. Set N8N_DEMO_PORT to move it, and pass the same value to demo-setup.sh, the integration tests and N8N_URL.

Tests

npm test              # unit tests, no instance required
npm run test:integration   # against the compose instance above

The integration suite skips the API-backed cases when N8N_API_KEY is unset, so it stays runnable on a bare docker compose up.

License

MIT