n8n-multi-instance – skill Viết lách & Nội dung cho agent AI

Working with multiple n8n instances over MCP

When to Use

Use this skill whenever one MCP connection can target multiple n8n instances, before instance-specific reads or writes, and whenever results suggest the session is aimed at the wrong environment.

Resolve the target from the discovered name, ID and URL; switch using the schema-supported name, verify it with a read-only health check, and state the resolved environment before mutations. Require explicit confirmation for credential create/update/delete operations, never print secret values, and stop on ambiguous targeting rather than guessing.

When the n8n_instances tool is available, the user has multi-instance mode on: one MCP

connection can reach several n8n instances (e.g. prod, staging, or one per client/team).

Every other n8n tool (n8n_get_workflow, n8n_list_workflows, n8n_update_partial_workflow,

n8n_manage_datatable, n8n_manage_credentials, n8n_executions, n8n_test_workflow, …) runs

against whichever instance this session is currently targeting. There is no per-call instance

argument: you change the target only by switching. Target the wrong instance and a read returns the

wrong data and a write lands in the wrong place — usually with no error (the one exception is an

ambiguous credential write, which fails closed; see below). So target deliberately.

If the tool is absent, multi-instance support is unknown. Verify the connected server and target using available read-only evidence before operating; do not infer single-instance access from a missing tool.

Golden rules

Six rules. Each prevents a class of silent misroute.

1. Discover first. Call n8n_instances({mode:"list"}) before acting so you know the instance

names and which one is current.

2. Switch by name to your target before doing work on a non-default instance:

n8n_instances({mode:"switch", name:"<instance name>"}). The match is case-insensitive.

3. Switch in its own turn. Never put a switch and a dependent operation in the **same

parallel tool-call batch**. Calls in one batch have no guaranteed order, so the dependent call

can be resolved against the *previous* instance before the switch's session state is visible.

Switch, let it return, *then* operate.

4. Verify before high-stakes ops. Immediately before creating/updating/deleting credentials

(and before destructive workflow edits), confirm current is the instance you intend — primary

check is n8n_instances({mode:"list"}). The system fail-closes only the *ambiguous* credential

case (rule 6); an explicit switch to the wrong instance still writes there silently, so this

check is on you.

5. An unexpected NOT_FOUND may be a wrong-instance misroute, missing permission or deletion. Don't

recreate the object. Re-check the current instance and retry (see Recovery).

6. **On INSTANCE_AMBIGUOUS, switch on *this* session, then retry.** The system is refusing to

write a secret because this session never picked a target itself. Comply — run switch here to

confirm the instance, then retry the write. Don't work around it or retry blindly.

Core workflow

1. n8n_instances({mode:"list"})                      # see available[] + current + default
2. n8n_instances({mode:"switch", name:"prod"})       # bind THIS session to "prod"
   → returns { previous, current }; confirm current.name == "prod"
3. (do your work) n8n_list_workflows / n8n_get_workflow / n8n_manage_datatable / ...
4. Before a credential write or a delete:
   n8n_instances({mode:"list"})  → re-confirm current, THEN n8n_manage_credentials({action:"create", ...})

To move to another instance, just switch again. The whole session follows the switch.

The n8n_instances tool

Two modes (mode is required and enum-validated):

• {mode:"list"} → { current, default, available }, no side effects.
• current and default are each one instance { id, name, url, isDefault } (or null).
• available is every instance, each with an extra isCurrent boolean. Match by name;

never hard-code id.

• {mode:"switch", name:"<name>"} → { previous, current }, and binds this session to the named

instance. name is case-insensitive.

Error envelope (from the n8n_instances tool)

Every error returns { error: "<CODE>", message, … }. The ones you'll actually hit:

| Code | When | What to do |

|---|---|---|

| UNKNOWN_INSTANCE | name matches no instance | Pick a name from the available list in the error payload and retry. |

| NAME_REQUIRED | switch with no name | Re-call with a name (the error lists the valid ones in available). |

| MULTI_INSTANCE_DISABLED | multi-instance mode is off | There's nothing to switch; use the n8n tools directly. The user can enable it at the n8n-mcp dashboard. |

| NO_SESSION | the request has neither an MCP session id nor a credential id | A selection has nowhere to land. Reconnect / initialize a session, then switch. |

| UNKNOWN_MODE | mode wasn't list/switch | Use list or switch. |

| INVALID_CONTEXT | server-side metadata missing | A server bug, not your input — report it. |

> Instance names can never be default, current, list, or switch (reserved), so you'll never

> see an instance literally named after a mode or field.

INSTANCE_AMBIGUOUS (from the credential-write path, not the tool)

A separate, higher-stakes error. It is not returned by n8n_instances — it's returned by the

server when you call n8n_manage_credentials to create/update/delete a credential and the target

instance is ambiguous: this session never switched on its own but inherited a switch made elsewhere

(a fan-out / reconnect), pointing at a non-default instance. Rather than risk writing a secret to

the wrong instance, the server blocks the write (it never reaches n8n, no quota is charged) and

returns:

{
  "error": "INSTANCE_AMBIGUOUS",
  "message": "… the session issuing this request never switched there itself … Re-run n8n_instances({mode:\"switch\", name:\"…\"}) on this session to confirm the target …",
  "lastSelected": { "id": "…", "name": "…" },
  "default":      { "id": "…", "name": "…" }
}

Fix: decide which instance you actually want (lastSelected is the inherited switch, default

is the account default), run n8n_instances({mode:"switch", name:"…"}) on this session, then

retry the write. See rule 6.

How targeting behaves (mental model)

• A switch binds this session to the chosen instance. The binding **persists for the rest of

the session and survives reconnects, idle, and backend deploys** (~24h, the MCP session lifetime)

— you should not need to re-switch before every call.

• Other sessions / terminals are independent: switching here does not move them.
• One session targets one instance at a time. There is no per-call instance argument; you

change the target only via switch.

• Reads and non-credential writes route to the currently-selected instance, silently — a

misroute produces wrong data or a NOT_FOUND, not an error.

• Credential writes are the one guarded case. They route the same way, except the server

fail-closes the *ambiguous* state (a session that never switched, recovered onto a non-default

instance) with INSTANCE_AMBIGUOUS. This is a safety net, not a substitute for rule 4: an

explicit switch to the wrong instance still writes there.

• If your selected instance is deleted (the user removes it mid-session), the next call silently

falls back to your default instance — no error. So default's data appearing where you expected

another instance's can look like "my data vanished." Re-list to see where you are.

Recovery playbook

| Symptom | What it usually means | Do this |

|---|---|---|

| INSTANCE_AMBIGUOUS on a credential create/update/delete | This session never switched itself; the system won't guess which instance to write the secret to | Run n8n_instances({mode:"switch", name:"<target>"}) on this session (the error names lastSelected and default — pick the one you want), then retry the write. Never retry blindly. |

| NOT_FOUND for a workflow/datatable/credential you know exists | You're pointed at the wrong instance — not that it was deleted | n8n_instances({mode:"list"}) → check current. If it's not your target, switch and retry. Do not recreate the object. |

| A read returns empty or unfamiliar data | Wrong-instance read, or a silent fallback to default after your instance was deleted | n8n_instances({mode:"list"}), confirm current, switch if needed, re-read before drawing conclusions. |

| UNKNOWN_INSTANCE on switch | The name is wrong (typo, or you guessed) | Read the available names in the error and switch to one of those. Names are case-insensitive. |

| n8n_health_check reports an instanceName you didn't expect | This session is

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