n8n Agents SkillSAFE

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---
name: n8n-agents
description: Design n8n AI agents the right way. Use when building or editing any @n8n/n8n-nodes-langchain.* AI node — an AI Agent, LLM chain, Text Classifier, or Information Extractor — and whenever the user mentions AI agents, LLM with tools, tool calling, $fromAI, system prompts, agent memory, sessionId, structured/JSON output, output parser, RAG, vector store, a chat assistant/bot, or human-in-the-loop review. Covers Agent-vs-chain-vs-classifier choice, the model/memory/tools/outputParser slots, tool names/descriptions as prompt, structured output with autoFix, memory, RAG, human review, and chat topologies.
---

# n8n Agents

The n8n AI Agent node (`@n8n/n8n-nodes-langchain.agent`) is a multi-turn LLM driver with sub-nodes for the model, memory, tools, and an optional output parser. This skill is the **deep** guide to designing agents and the LangChain family around them. For the high-level "where an agent fits in a workflow" picture, see **n8n-workflow-patterns** `ai_agent_workflow.md` — this skill goes one level down into *how to build it well*.

For node-type formats: in workflow JSON the LangChain nodes use the long `@n8n/n8n-nodes-langchain.*` form (`.agent`, `.lmChatOpenAi`, `.memoryBufferWindow`, `.outputParserStructured`, `.toolWorkflow`, `.toolHttpRequest`, `.toolCode`). When you call `get_node` / `validate_node`, use the **short** form (`nodes-langchain.agent`). See **n8n-mcp-tools-expert** for the format rules.

---

## Pick the right node first

Reaching for an Agent when the task is one-shot classification or extraction is the most common over-build. Decide before you wire anything:

| You need to... | Use | Why |
|---|---|---|
| Call tools, reason over multiple turns, or hold memory | **AI Agent** (`.agent`) | The full loop: model + tools + memory + optional parser. Also a fine default when you'd rather standardize. |
| One-shot text in → text out, no tools | **Basic LLM Chain** (`.chainLlm`) | No agent loop, easier to debug. Still accepts an `outputParserStructured` sub-node. |
| Route a natural-language input to one of **N branches** | **Text Classifier** (`.textClassifier`) | ONE node, N output handles, downstream wires directly into each. Not Agent + Switch. |
| Pull structured fields out of free text | **Information Extractor** (`.informationExtractor`) | Purpose-built field extraction with a schema. |
| 3-way positive/neutral/negative split | **Sentiment Analysis** (`.sentimentAnalysis`) | Built-in branch outputs. |
| Condense a long document | **Summarization Chain** (`.chainSummarization`) | Map-reduce summarization built in. |
| Generate an image / audio / video | **The provider's native single-call node** (OpenAI, Gemini, ElevenLabs...) | NEVER wrap media generation in an Agent — see "Binary and the agent boundary". |

**Text Classifier detail (the Agent + Switch anti-pattern):** every category needs both a **name AND a description**. The model routes against the *description*, not the name — a category with no description gets picked by coin-flip. Set `options.enableAutoFixing: true` for robustness on edge inputs. One node, N branches, done. Reaching for an Agent that "decides" then a Switch that "routes" is two nodes plus prompt boilerplate for what Text Classifier does natively.

Chat-model nodes (`.lmChatOpenAi`, `.lmChatAnthropic`, `.lmChatOpenRouter`, ...) are **sub-nodes** — they don't run standalone. They wire into a chain, agent, classifier, or extractor via the `ai_languageModel` connection.

---

## The sub-node pattern

The Agent has a **main input** (the prompt / user message) and up to four **sub-node slots**, each wired by its own `ai_*` connection type:

| Slot | Connection type | Required? | Node example |
|---|---|---|---|
| **model** | `ai_languageModel` | Yes | `.lmChatOpenAi`, `.lmChatAnthropic`, `.lmChatOpenRouter` |
| **memory** | `ai_memory` | Optional | `.memoryBufferWindow`, `.memoryPostgresChat` |
| **tools** | `ai_tool` | Optional (but the point of an agent) | `slackTool`, `.toolWorkflow`, `.toolHttpRequest`, `.toolCode` |
| **outputParser** | `ai_outputParser` | Optional | `.outputParserStructured` |

A sub-node connects FROM itself TO the agent. In workflow JSON the connection lives on the **sub-node**, keyed by the `ai_*` type:

```json
"Main LLM": {
  "ai_languageModel": [[{ "node": "AI Agent", "type": "ai_languageModel", "index": 0 }]]
},
"Simple Memory": {
  "ai_memory": [[{ "node": "AI Agent", "type": "ai_memory", "index": 0 }]]
},
"Search customer DB": {
  "ai_tool": [[{ "node": "AI Agent", "type": "ai_tool", "index": 0 }]]
}
```

Multiple tools all connect into the same `ai_tool` index 0 — they stack, they don't fan into separate indices. With `n8n_update_partial_workflow` you wire each with an `addConnection` op using `sourceOutput: "ai_tool"`. The agent puts its final answer in **`$json.output`** (not `.text`, not `.response`) — downstream nodes read `{{ $json.output }}`.

See **EXAMPLES.md** for a complete stateless agent-core node-object snippet.

---

## Two non-negotiables

1. **Tool names and descriptions ARE part of the prompt.** The model picks a tool by reading its name and description — nothing else. A tool named `tool1` with an empty description is invisible to the model: it skips it, mis-selects it, or hallucinates parameters. There's usually no error — just an agent that "won't use my tool". Treat both like API design. → **TOOLS.md**
2. **Structured output must parse AND autoFix.** An `outputParserStructured` with `autoFix: true` and a **coding-capable fixer model** is the production pattern. Without autoFix, one malformed JSON response halts the whole workflow. → **STRUCTURED_OUTPUT.md**

---

## Strong defaults

- **Per-tool usage goes in the tool description, not the system prompt.** Anything about *how to call this specific tool* belongs with the tool, so it travels across agents and keeps the system prompt focused. → **SYSTEM_PROMPT.md**
- **Sub-workflow tools (`.toolWorkflow`) for a

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

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Findings (2)

1. **Plumb a stable key through.** Memory buckets by whatever you bind to `sessionKey`. The Chat Trigger fills `sessionId` automatically. For other triggers, derive a stable identifier (Slack `thread_

**Messages past the window are removed entirely.** Once the buffer fills, the oldest exchanges are dropped and the agent can't recall, search, or even know they existed. If a user said something 60 tu

Gates applied: no_behavioural_pass.

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