# AI skills for the back office: teach AI your way of working > An AI skill is a reusable set of instructions that teaches an AI app one task, such as checking an invoice or writing a reminder in your tone. Unlike a prompt you paste every time, the AI loads the skill by itself when the task fits. ChatGPT offers skills in Business, Enterprise and Edu workspaces, Claude on every plan (as of 08/10/2026), Grok since 18/05/2026 (as of 20/10/2026). Source: https://back-bone.io/en/blog/ki-skills-backoffice Published: 2026-10-21 · Updated: 2026-10-22 Category: Guides An AI skill is a reusable set of instructions that teaches an AI app one task, such as checking an invoice or writing a reminder in your tone. Unlike a prompt you paste every time, the AI loads the skill by itself when the task fits. ChatGPT offers skills in Business, Enterprise and Edu workspaces, Claude on every plan (as of 08/10/2026), Grok since 18/05/2026 (as of 20/10/2026). **TL;DR · Key facts** - **A skill** is a folder with a `SKILL.md` text file: what to do, in which steps, in which format, with which checks. - **Skill vs. prompt:** a prompt is typed or pasted each time; a skill waits in the background and is picked up when the task matches. - **Where it works (as of 08/10/2026, Grok 20/10/2026):** ChatGPT in Business, Enterprise and Edu workspaces, if the owner allows it; Claude on Free, Pro, Max, Team and Enterprise; Grok on the web, in its apps and in Grok Build. The format is an open standard, so one skill can travel between tools. - **Good first skills:** routines you repeat with the same rules: invoice checks, reminders, hours to invoice lines, month-end. - **Rules change, skills must too:** date every skill and re-check it when the law, a rate or your own process changes. ## What is a skill, and how is it different from a prompt? A skill packages **how you do a task**: the steps, the output format, your tone, the checks at the end. It is a folder with one required text file, `SKILL.md`, written in plain Markdown. It can also hold templates and examples. The difference from a prompt is about **when** the instructions are used: - **Prompt:** you write or paste it in every chat. Good for one-off questions. - **Custom instructions or project:** standing background that is always loaded. Good for "who I am and who my clients are". - **Skill:** a task-specific procedure. The AI first sees only its name and short description. When your request matches, it loads the full text and follows it. That keeps chats light, even with many skills. Like handing a new colleague the reminder process sheet once, so you stop explaining it every Monday. Skills are an open format. Anthropic created it and released it as an open standard; many tools now read it (agentskills.io, as of 08/10/2026). A skill you write once works in other apps too. ## Where do skills work today? Status as of 08/10/2026 (Grok: 20/10/2026), from the vendors' own pages. Menus and plans change, so the vendor page wins. | Tool | Skills | What to know | | --- | --- | --- | | ChatGPT | Business, Enterprise, Edu | The workspace owner decides who may create, use, share and install skills; in some workspaces they start switched off. ChatGPT can draft a skill from a description, and you can upload skills built elsewhere. | | Claude (web, desktop) | Free, Pro, Max, Team, Enterprise | Needs code execution switched on. Upload a ZIP of the skill folder under Customize > Skills. Uploaded skills stay private until you share them. | | Claude, organisations | Team, Enterprise | Owners can provision skills for everyone; members can switch them on or off. | | Claude Code | Yes | Skills sync when you sign in with your Claude account. | | Grok (web, iOS, Android) | Since 18/05/2026; xAI names no plans | Built-in skills for Word, PowerPoint, Excel and PDF plus a Skill Creator; your own skills by chat, file upload or written from scratch. Whether a `SKILL.md` folder from other apps works there is not confirmed. In Grok Business, admins set how widely skills can be shared. | | Grok Build (CLI) | Yes | Reads `SKILL.md` folders from `~/.grok/skills/` and `~/.agents/skills/`, including skills in Claude Code format. Skills from our [skill library](https://back-bone.io/en/tools/skill-library) work there. | OpenAI's pages differ on plans and beta status, and Free, Plus and Pro are not confirmed, so check your own settings. Also: skills from strangers are instructions your AI will follow. Install only skills you have read or that come from a source you trust. If your tool has no skills, the text of a skill still works as instructions you paste into a chat, a project or a custom GPT. ## Which back-office routines make good skills? A routine is a good skill if you do it **again and again, with the same rules, and can describe a good result**. Typical candidates for freelancers, studios, agencies and small businesses in Germany and Austria: 1. **Invoice check.** Does the invoice have all mandatory details? Rules differ: see [Invoice requirements Germany](https://back-bone.io/en/blog/pflichtangaben-rechnung-deutschland) and [Austria](https://back-bone.io/en/blog/pflichtangaben-rechnung-oesterreich). Ready-made skill: [Invoice checker DE/AT](https://back-bone.io/en/tools/skill-library#invoice-check). 2. **Reminders in your tone.** Friendly first nudge, firm second, formal third, each with the right deadline. Background: Payment reminders. Ready-made skill: [Payment reminders in your tone](https://back-bone.io/en/tools/skill-library#reminder-writer). 3. **Hours to invoice lines.** Turn raw time entries into lines a client understands. Ready-made skill: [Invoice writer DE/AT](https://back-bone.io/en/tools/skill-library#invoice-writer). 4. **Quote from a brief.** Scope, items, assumptions, terms. 5. **Receipt sorter.** Name, date and file receipts; list what is missing for the month. Ready-made skill: [Monthly receipt routine](https://back-bone.io/en/tools/skill-library#receipt-routine). 6. **Month-end checklist.** The same twenty minutes every month. Ready-made skill: [Month-end checklist](https://back-bone.io/en/tools/skill-library#month-end-checklist). 7. **Handover note for your tax adviser.** What happened, what is open, what you need to ask. Poor candidates: one-off tasks, anything where the rules are unclear to you, and decisions that should stay with you, such as whether to write off an invoice. Every legal skill should say which country it covers (Germany, Austria or both), carry a date and keep a human in the loop. AI prepares, you approve. These five are ready in our free [skill library](https://back-bone.io/en/tools/skill-library), to download and use with or without Backbone. ## How do you write a skill that works? Keep it short: 1. **Name and one-line description.** The description decides when the AI picks the skill, so name the task and the trigger: "Use when checking an invoice before sending." 2. **Inputs.** What the AI needs: the invoice text, the country, the client type. 3. **Steps.** Numbered and concrete. 4. **Output format.** A table, a short email, a checklist. 5. **Final checks.** "List anything you could not verify. Never invent a VAT ID." Then test it on three real cases, including one where the answer should be "something is missing". Fix the wording, test again. ## How do you keep a skill correct when rules change? A skill is a copy of your rules at one point in time. Treat it like a document with an owner: - **Date it.** Put "checked on" and the country in the skill itself. - **Keep facts out of the steps.** Put rates, thresholds and deadlines in one clearly marked block, so an update touches one place. Late-payment interest and base rates are reset on fixed dates (the current ones are valid until 31 Dec 2026), see [Late-payment interest](https://back-bone.io/en/blog/verzugszinsen-berechnen-mahnung-muster). - **Re-check on triggers.** A change in law (for example the phased e-invoice rules in Germany, see E-invoicing Germany), a new year, a new client type, or a wrong answer. - **Add a rule of doubt.** "If the date of this skill is older than twelve months, say so." - **Use one source.** Keep the master copy in one place and re-upload it everywhere, instead of editing copies. Our [library skills](https://back-bone.io/en/tools/skill-library) carry a "checked on" date and are re-checked together with the guides here. ## What changes when a skill can reach your real data? A skill on its own works on what you paste in. Connect Backbone to your AI app and the same skill works on your real invoices, hours and receipts. The skill knows how you work, the connector has the data. "Check this month's invoices" without copying ten PDFs into a chat. Asking ChatGPT or Claude to prepare something creates a draft you review, and the AI asks you before it sends. How the connection works is in [What is MCP?](https://back-bone.io/en/blog/was-ist-mcp). > My goal is to optimise and automate back-office tasks so that we founders can focus on what matters most. > > Automating back-office work with AI agents and AI integrations is the future – that's why I built Backbone! ## How Backbone does it Your back office in the chat. In the app, or in a chat with ChatGPT, Claude and many more. 1. **Ask the company wiki** Ask instead of searching. The answer comes from your wiki. 2. **Create the invoice** Say what goes on it. You approve. 3. **Bill your hours** What you tracked goes on the invoice. 4. **Send the reminder** You approve. Only then does it go out. 5. **Receipts matched automatically** Upload the statement. Clear matches assign themselves. 6. **Off to your bookkeeper** Month complete. One link, done. ## Frequently asked questions ### Do I need to code to write a skill? No. A skill is a text file in plain language. In both ChatGPT and Claude you can also describe the job and let the AI draft the skill, then edit it. ### Is a skill the same as a custom GPT or a Claude project? No. Projects and custom GPTs hold standing background and instructions. A skill is a procedure that is loaded only when the task matches. They work well together. ### Will one skill work in ChatGPT and Claude? Both support the open Agent Skills format with a `SKILL.md` file (as of 08/10/2026), so a skill can often move between them. Grok Build reads `SKILL.md` folders too; whether they work in the Grok app is not confirmed (as of 20/10/2026). Test it in each tool, because features differ. ### Are skills safe? A skill is text the AI follows. A bad one can steer it wrongly. Read a skill before you install it and take it only from sources you trust. Never put passwords or bank details into a skill. ### Can I put client data into a skill? Better not. Keep the skill about the process. Share client data only in the chat, and only on an AI plan with a data processing agreement (Art. 28 GDPR). More in [AI and GDPR](https://back-bone.io/en/blog/ki-dsgvo-selbststaendige). ### Does Backbone cost extra for skills? The connector is part of every Backbone plan. The [skill library](https://back-bone.io/en/tools/skill-library) is free. Your AI provider's costs depend on your contract there. ### Where do I find ready-made skills? In our free [skill library](https://back-bone.io/en/tools/skill-library), as ZIP downloads. The AI connector is live too. **Your skills, on real numbers** Connect Backbone to ChatGPT or Claude and let your skills handle invoices, hours and receipts. 7-day trial, card required. - [Try for 7 days](https://back-bone.io/en/sign-up) --- General information, not legal or tax advice and no review of your case. Details on providers and laws can change. For your case, follow your tax adviser. Checked on 20/10/2026 Sources: Anthropic Help Center, Using skills in Claude (read 08/10/2026) · Anthropic Help Center, What are skills (read 08/10/2026) · Agent Skills open standard (agentskills.io, read 08/10/2026) · OpenAI Help Center, Skills in ChatGPT (08/10/2026) · OpenAI Academy, Skills in ChatGPT (read 08/10/2026) · xAI News, Grok Skills (read 20/10/2026) · xAI Docs, Grok Build Skills, Plugins & Marketplaces (read 20/10/2026) · xAI Docs, Grok Management (read 20/10/2026)