n8n Multi-Instance Skill

Expert guidance for working with the n8n-mcp n8n_instances tool — choosing and switching which n8n instance an MCP session targets, verifying the target before high-stakes work, and recovering from misroutes. Only relevant when the account has multi-instance mode on (the n8n_instances tool is present); single-instance accounts never need it.

The core problem this skill solves

In multi-instance mode, one MCP connection reaches several n8n instances (e.g. prod, staging, or one per client). Every n8n tool — workflows, datatables, credentials, executions — routes to whichever instance the session is currently targeting, uniformly and with no per-call instance argument. There is no error when you operate on the wrong one: you simply read the wrong data, or get a NOT_FOUND that looks like a deletion. The danger is silence, so the skill is about targeting deliberately and verifying before it matters.

What This Skill Teaches

Core concepts

1. Discover, then switch by name — n8n_instances({mode:"list"}) to see current/default/available, then {mode:"switch", name} (case-insensitive)
2. Switch in its own turn — never batch a switch with a dependent call; parallel-batch ordering isn't guaranteed, so the dependent call can resolve against the previous instance
3. Verify before high-stakes ops — re-list (or n8n_health_check, which echoes instanceName) immediately before any credential create/update/delete; nothing downstream re-checks
4. NOT_FOUND ≈ misroute, not deletion — verify the instance and retry; never recreate
5. The binding persists — per-session, surviving reconnects/idle/deploys (~24h); you don't re-switch before every call
6. Deleted-instance fallback — if your selected instance is removed mid-session, calls silently fall back to default

Top traps this skill prevents

1. Treating a NOT_FOUND as "it was deleted" and recreating an object that lives on another instance
2. Writing a credential to the wrong instance after an explicit (wrong) switch — current wasn't verified right before the write, and the ambiguous-write fail-close doesn't catch this case
3. Racing a switch against dependent work in the same parallel tool-call batch
4. Assuming a per-call instance argument exists (it doesn't — only switch changes the target)
5. Misreading a silent fallback to default (after an instance was deleted) as missing data

Skill Activation

Activates when:

• The n8n_instances tool is available (multi-instance mode is on)
• The user mentions multiple n8n instances/environments (prod vs staging, several teams/clients)
• A workflow/datatable/credential/execution call returns an unexpected NOT_FOUND or wrong/empty data
• You're about to create/update/delete a credential on a multi-instance account

Example queries:

• "I have a prod and a staging n8n — create this credential on staging, not prod."
• "n8n_get_workflow says NOT_FOUND but I can see the workflow in the UI. What's wrong?"
• "How do I copy a workflow from one of my n8n instances to another?"
• "My agent keeps editing the wrong n8n instance — how do I pin it to the right one?"
• "n8n_list_workflows is showing workflows I don't recognize."

File Structure

SKILL.md

The full skill content — loaded when the skill activates.

• What multi-instance mode is, and when to ignore this skill
• Five golden rules (discover, switch-by-name, switch-in-own-turn, verify-before-writes, NOT_FOUND≈misroute)
• The n8n_instances tool: modes, real response shapes, the real error envelope
• Mental model: per-session binding + persistence, uniform resolution, deleted→default fallback
• Recovery playbook (symptom → cause → fix)
• Credential operations as the highest-stakes case
• Copy-between-instances task; quick reference; cross-skill integration

This skill is self-contained in one file — no reference files — because the surface is small and the rules are tightly coupled.

Quick Reference

# See instances + where you are
n8n_instances({ mode: "list" })   → { current, default, available:[{id,name,url,isDefault,isCurrent}] }

# Change the session's target (own turn, then operate)
n8n_instances({ mode: "switch", name: "staging" })   → { previous, current }

# Confirm before a credential write
n8n_instances({ mode: "list" })   # or n8n_health_check → instanceName
n8n_manage_credentials({ action: "create", ... })

n8n_instances error codes: UNKNOWN_INSTANCE, NAME_REQUIRED, MULTI_INSTANCE_DISABLED, NO_SESSION, UNKNOWN_MODE, INVALID_CONTEXT. A credential create/update/delete can additionally fail closed with INSTANCE_AMBIGUOUS when the target is ambiguous — switch on this session to confirm, then retry. The fail-close only covers the ambiguous case, so still verify current before any credential write.

Integration with Other Skills

n8n-mcp-tools-expert: owns the n8n_manage_credentials tool (CRUD, getSchema) and the secrets-via-credential-system rule. This skill adds the "which instance?" layer on top.

using-n8n-mcp-skills: the router — names which skill owns each step of a build.

Success Metrics

After using this skill, you should be able to:

• List instances and read current before acting
• Switch by name, in its own turn, and confirm the result
• Verify current immediately before any credential create/update/delete
• Diagnose an unexpected NOT_FOUND as a misroute and recover without recreating anything
• Copy a workflow or credential between instances safely
• Recognize the silent fallback to default when a selected instance is deleted

Version

Version: 1.0.0 Compatibility: n8n-mcp servers exposing the n8n_instances tool (multi-instance mode). On single-instance accounts the tool is absent and this skill does not apply.

Remember: there is no per-call instance argument, and a wrong target is usually silent — the one exception is an ambiguous credential write, which fails closed with INSTANCE_AMBIGUOUS. Discover, switch by name in its own turn, and verify current before anything that writes — credentials above all.