# n8n intermediate: API calls, webhooks, expressions and error handling on one page > A free one-page n8n intermediate cheat sheet: HTTP Request settings, GET vs POST, webhook URLs, expressions, items, AI approval and error handling. Source: https://learn.ynteractive.com/content/cheat-sheets/n8n-intermediate · Updated 2026-10-17 · Free from Stepthrough (https://learn.ynteractive.com) [Tool cheat sheet](https://learn.ynteractive.com/content/cheat-sheets#kind-tool) · One page · US letter · [n8n](https://learn.ynteractive.com/content/tool/n8n) By [Robert Breen](https://learn.ynteractive.com/content/about) · Published October 17, 2026 · From the free lesson [n8n: Call Any API with the HTTP Request Node](https://learn.ynteractive.com/content/n8n-http-request-node-call-any-api) A free one-page n8n intermediate cheat sheet: HTTP Request settings, GET vs POST, webhook URLs, expressions, items, AI approval and error handling. [Download the free PDF (76 KB)](https://learn.ynteractive.com/content/cheat-sheets/n8n-intermediate.pdf)Print this sheet Free, no sign-up and no email needed. It prints on one letter-size page; the whole sheet is below. *▶*StepthroughFree printable cheat sheet · learn.ynteractive.com n8n intermediate: API calls, webhooks, expressions and error handling on one page The settings that turn a first n8n workflow into one the business runs on, from the free n8n Intermediate course. ## HTTP Request: call any API **Method** **GET** reads and changes nothing. **POST** sends data to create something. **URL** The address from the app's API docs, like `https://jsonplaceholder.typicode.com/users`. **Send Query Parameters** Narrow a GET: Name `username`, Value `Samantha` adds `?username=Samantha`. **Send Body** For POST: **JSON**, **Using Fields Below**, one field per value. **Authentication** A saved credential. Never paste a key into the URL or body. ## Data and expressions **Item** One record. A node runs once per item. **Expression** `{{ $json.email }}` = this item's email. Drag a field from INPUT onto a box to make one. **Output views** **Schema**, **Table** and **JSON** show the same data three ways. ## Triggers that run without you **Schedule Trigger** At a set time, in the workflow's time zone. **Webhook Test URL** Listens only while you click **Listen for test event**. **Webhook Production URL** Listens all the time after **Publish**. This one goes in the live form. ## Safe AI and error handling - Save AI replies as **Gmail drafts**; a person sends them. - An **error workflow** (Error Trigger + email) tells you when any workflow fails. - **Retry On Fail** for flaky steps; **Executions** to retry a failed run. - Green checks mean a node ran. Check the real result: the sheet, the inbox, the CRM. **Remember:** Test with Execute step on real-looking data, check where the result lands, then Publish. Every change after that needs another Publish. Practice it free: [n8n: Call Any API with the HTTP Request Node](https://learn.ynteractive.com/modules/n8n-http-request-api) at learn.ynteractive.com/modules/n8n-http-request-api. This sheet: learn.ynteractive.com/content/cheat-sheets/n8n-intermediate. Harbor Lane Marketing is a made-up business from the lesson. By Robert Breen, October 17, 2026. ## Practice it in the free lesson **n8n: Call Any API with the HTTP Request Node**. Connect n8n to any app with an API: GET a CRM's client list, filter it with a query parameter, then POST a note back using an expression. Free practice API, no key needed. You do every step yourself in a practice copy of n8n, it checks your work as you go, and “Do it for me” finishes any step you get stuck on. Free, and nothing touches your real accounts. [Start the free lesson](https://learn.ynteractive.com/modules/n8n-http-request-api) [Or read the full step-by-step guide](https://learn.ynteractive.com/content/n8n-http-request-node-call-any-api) ## Lessons on this sheet - [n8n: Call Any API with the HTTP Request Node](https://learn.ynteractive.com/content/n8n-http-request-node-call-any-api): Connect n8n to any app with an API: GET a CRM's client list, filter it with a query parameter, then POST a note back using an expression. Free practice API, no key… - [n8n: Read, Add and Update Google Sheets Rows with an AI Step](https://learn.ynteractive.com/content/n8n-google-sheets-read-append-update): Learn n8n's three core Google Sheets moves on a made-up request list: read the rows, add a new one without duplicates, then let an AI step write a description and… - [Get Your Daily Revenue Total by Email, Automatically, using n8n](https://learn.ynteractive.com/content/n8n-schedule-trigger-google-sheets-daily-report): Stop spending 20 minutes every evening adding up the day by hand. In n8n, a Schedule Trigger runs at 5pm, Google Sheets pulls today's jobs, Summarize totals the revenue… - [Webhooks and Forms in n8n: Capture Data from Anywhere](https://learn.ynteractive.com/content/n8n-webhook-and-form-trigger-tutorial): Stop losing quote requests between inboxes. Build a form n8n hosts for you, catch entries from your own website with a webhook, and save every request to one Google… - [n8n AI Email Responder: Draft Gmail Replies Automatically](https://learn.ynteractive.com/content/ai-email-responder-gmail-drafts-n8n): Build an n8n agent that watches your Gmail, reads each new customer email, and writes a reply as a draft in the same thread, ready for you to check and send. - [Get Alerted When an n8n Automation Fails, and Let It Retry by Itself](https://learn.ynteractive.com/content/n8n-error-handling-retry-on-fail-error-workflow): A silent failure means a stale price sheet and wrong quotes. In n8n, build an error workflow that emails you, make a flaky step retry by itself, send its failures down… ## Related terms Plain-English definitions, each with an example from a free lesson. [HTTP Request node](https://learn.ynteractive.com/content/glossary/http-request-node) · [Query parameter](https://learn.ynteractive.com/content/glossary/query-parameter) · [Request body (payload)](https://learn.ynteractive.com/content/glossary/request-body) · [Expression](https://learn.ynteractive.com/content/glossary/expression) · [Item (n8n)](https://learn.ynteractive.com/content/glossary/item) · [Credential](https://learn.ynteractive.com/content/glossary/credential) · [Test URL vs production URL](https://learn.ynteractive.com/content/glossary/webhook-test-url-vs-production-url) · [Error handling](https://learn.ynteractive.com/content/glossary/error-handling) [The full AI glossary](https://learn.ynteractive.com/content/glossary) ## Related prompts - [AI agent system message prompt](https://learn.ynteractive.com/content/prompts/agent-system-message-draft-prompt): Draft the system message for an n8n AI Agent: who it is, what it knows, its rules and how it writes, including a rule never to… - [Daily priorities plan prompt](https://learn.ynteractive.com/content/prompts/daily-priorities-plan-prompt): Paste your to-do list and fixed times and get a realistic plan for today: top three, time blocks, a buffer, and what to move to… - ["Do you service my area?" reply prompt](https://learn.ynteractive.com/content/prompts/service-area-question-reply-prompt): Answer "do you cover my town?" from your real service area list: a clear yes with how to book, a kind no, or a request for the… - [FAQ from customer emails prompt](https://learn.ynteractive.com/content/prompts/faq-from-customer-emails-prompt): Turn a batch of customer emails into an FAQ: the questions people really ask, in their words, answered only from your facts… [All free prompt templates](https://learn.ynteractive.com/content/prompts) ## More cheat sheets - [AI Email Responder in n8n Cheat Sheet](https://learn.ynteractive.com/content/cheat-sheets/ai-email-responder-n8n): A free one-page cheat sheet: n8n watches Gmail, an AI agent reads each customer email and saves a reply as a draft in the same thread. - [AI Email Drafts Safety Cheat Sheet](https://learn.ynteractive.com/content/cheat-sheets/ai-email-drafts-safety): A free one-page cheat sheet: let AI write email drafts, not sends. Give it facts and rules, keep private data out and check every promise. - [Check Every Promise in an AI Reply: Cheat Sheet](https://learn.ynteractive.com/content/cheat-sheets/check-every-promise): A free one-page cheat sheet: give ChatGPT the thread and your numbered facts, ask for a promise-by-promise table, fix what it flags, then send. [All free cheat sheets](https://learn.ynteractive.com/content/cheat-sheets) · [All free tutorials](https://learn.ynteractive.com/content)