/n8n-workflow-patterns

AI Agent Workflow Pattern

Use Case: An AI agent with tool access, memory, and reasoning sits inside a larger workflow — trigger feeds it, it decides and acts, output flows on.

For agent design depth, use the n8n-agents skill. This file covers where an AI agent sits in a workflow's architecture (trigger → agent → output, the ai_* sub-node connection types). The n8n-agents skill owns the design rules: tool selection and $fromAI parameters, the system-prompt vs tool-description split, structured output with autoFix, memory and sessionId, human-in-the-loop review, RAG, and chat shell/core/sub-agent topologies. Start there when building or debugging an agent.

Pattern Structure

Trigger → AI Agent (Model + Tools + Memory + optional Output Parser) → [Process Response] → Output

Key Characteristic: AI-powered decision making with tool use. From the workflow angle, an agent is one node with a main input/output plus ai_* sub-node slots — it slots into the same trigger → process → deliver spine as every other pattern.

Core AI Connection Types

Agent workflows wire sub-nodes into the agent with dedicated ai_* connection types — not the regular main connection. This is the single most important architectural fact: a tool wired to main is invisible to the agent (and validate_workflow flags it as disconnected).

Wiring direction: a sub-node connects FROM itself TO the agent, and the connection lives on the sub-node keyed by its ai_* type. With n8n_update_partial_workflow you add each with an addConnection op using sourceOutput: "ai_tool" (or "ai_languageModel", etc.). Multiple tools all stack on the same ai_tool index 0.

Core Components

The agent has a main input (the user message / prompt) and up to four sub-node slots:

1. Trigger — Chat Trigger (chat UI/streaming), Webhook (API), Manual (testing), or Schedule (periodic). Feeds the agent's main input.
2. Language Model (ai_languageModel, required) — the reasoning engine. One chat-model sub-node; a second can be wired as a fallback.
3. Tools (ai_tool, optional but the whole point) — ANY node can be a tool. HTTP Request, a database node, a sub-workflow, Code, or a pre-built tool node connects via the ai_tool port and the agent calls it by name.
4. Memory (ai_memory, optional) — maintains conversation context across turns, keyed by a sessionKey.
5. Output Parser (ai_outputParser, optional) — forces structured JSON instead of free text.

Critical output fact: the AI Agent node puts its final answer in $json.output — not $json.text or $json.response. Downstream nodes reference {{ $json.output }}.

Fan-out tip: when several agents run in parallel (e.g. multiple research agents feeding one report), avoid funneling them into a Merge node — Merge combineAll does a cross-product and mishandles inputs arriving at different times (often yielding 0 output). Either have each agent deliver its own output directly, or collect same-shaped items with an Aggregate node followed by a Code node for formatting.

For the deep slot mechanics — tool types, $fromAI parameters, memory configuration, parser schemas — see n8n-agents.

Common Use Cases

Short architecture sketches. Each is a trigger → agent → output spine; the agent's sub-nodes are listed under it.

1. Conversational Chatbot

Webhook (chat message) → AI Agent → Webhook Response
                          ├─ Chat Model (ai_languageModel)
                          ├─ HTTP Request Tool — search knowledge base (ai_tool)
                          ├─ Database node — query orders (ai_tool)
                          └─ Window Buffer Memory, keyed on session_id (ai_memory)

2. Document Q&A (RAG)

Setup (run once):  Read Files → Text Splitter → Embeddings → Vector Store
Query (recurring): Webhook → AI Agent → Webhook Response
                              ├─ Chat Model (ai_languageModel)
                              ├─ Vector Store Tool — search docs (ai_tool)
                              └─ Buffer Memory (ai_memory)

3. Data Analysis Assistant

Webhook (data question) → AI Agent → Code (chart data) → Webhook Response
                          ├─ Chat Model (ai_languageModel)
                          ├─ Postgres node, read-only user (ai_tool)
                          └─ Code Tool — analysis (ai_tool)

4. Workflow Automation Agent

Slack (slash command) → AI Agent → Slack (status)
                        ├─ Chat Model (ai_languageModel)
                        ├─ HTTP Request Tool — GitHub API (ai_tool)
                        ├─ HTTP Request Tool — Deploy API (ai_tool)
                        └─ Postgres node — deployment logs (ai_tool)

5. Email Processing Agent

Email Trigger → AI Agent → Email (auto-response) → Slack (notify team)
                ├─ Chat Model (ai_languageModel)
                ├─ Vector Store Tool — similar tickets (ai_tool)
                └─ HTTP Request Tool — create Jira ticket (ai_tool)

For the content of these (tool descriptions, system prompts, schema design), see n8n-agents EXAMPLES.md.

What the deep design lives in n8n-agents

This file is the workflow-architecture view. The design depth below is owned by n8n-agents — go there, don't duplicate it here:

• Tool configuration (the four tool types, native vs .toolWorkflow vs HTTP Request Tool vs MCP Client, $fromAI() anatomy, tool names/descriptions as prompt) → n8n-agents TOOLS.md, and SUBWORKFLOW_AS_TOOL.md for wiring a sub-workflow as a tool.
• Memory configuration (buffer/window/postgres/redis, contextWindowLength, sessionId handling per trigger) → n8n-agents MEMORY.md.
• Agent vs chain vs classifier choice, prompt engineering, system-prompt vs tool-description split → n8n-agents SYSTEM_PROMPT.md (and the SKILL.md "Pick the right node" table).
• RAG chains, structured output, streaming, fallback models → n8n-agents RAG.md and STRUCTURED_OUTPUT.md.
• Human review / gating destructive tools → n8n-agents HUMAN_REVIEW.md.
• Error handling (tool failures, LLM API errors, retries, error workflows) → n8n-error-handling, plus the agent-specific notes in n8n-agents.
• Performance, security, testing, common gotchas → n8n-agents (anti-patterns table and quick-reference checklist) for the agent-specific ones; the workflow lifecycle (test → validate → activate) is in this skill's SKILL.md "Workflow lifecycle" section.

One workflow-architecture safety note worth restating here: any tool that fetches third-party content (HTTP Request, web search, MCP Client, scrapers) can return attacker-controlled text that reaches the agent's context — indirect prompt injection. If the agent can both read the internet AND take an action the user can't undo, put a guardrail (human review, read-only scopes) between them. The detail lives in n8n-agents HUMAN_REVIEW.md and the n8n-agents anti-patterns.

Checklist for AI Agent Workflows

Architecture-level checks (the design-level checklist lives in n8n-agents):

• Trigger feeds the agent's main input
• Language model wired via ai_languageModel (required)
• Tools wired via ai_tool ports — NOT main (a tool on main is disconnected from the agent)
• Memory wired via ai_memory, keyed on a stable sessionKey from the trigger — when conversation context is needed
• Output parser wired via ai_outputParser — when downstream needs strict JSON
• Downstream nodes read the response from {{ $json.output }}
• Parallel agents collected with Aggregate, not Merge combineAll
• Validated with validate_workflow (confirms sub-nodes sit on ai_*, not main)
• Tested and activated per the lifecycle (see SKILL.md "Workflow lifecycle" section)

Summary

Key Points:

1. An agent is one node with a main input/output plus ai_* sub-node slots — it fits the standard trigger → process → deliver spine.
2. 8 AI connection types — wire the model with ai_languageModel, tools with ai_tool, memory with ai_memory, parsers with ai_outputParser. Never main.
3. ANY node can be a tool — connect it via the ai_tool port.
4. The response is in $json.output.
5. For all design depth — tools, memory, prompts, structured output, RAG, human review, chat topologies — go to n8n-agents.

Pattern: Trigger → AI Agent (Model + Tools + Memory + optional Parser) → Output

Related:

• n8n-agents — the deep agent design guide (tools, memory, prompts, structured output, RAG, human review, chat topologies)
• webhook_processing.md — receiving chat messages
• http_api_integration.md — tools that call APIs
• database_operations.md — database tools for agents
• SKILL.md "Workflow lifecycle" section — test, validate, and activate the workflow
• n8n-error-handling — tool-failure and LLM-error handling