Once you graduate from Claude’s online chat feature (yes, it’s time) and are ready for the big leagues, you’ll start realizing that there are more features — and nuances — that you must contend with.

One of those nuances is understanding the difference between instructions and skills. Strap in, because this one’s going to be boring, but also crucial.

To skill? Or to instruct?

Instructions are a single block of always-on text, set once in an app's settings and applied automatically to every conversation in that app. This is where a short, durable rule belongs. I equate it to the do’s and don’ts you teach every new hire (ex: every hardcode must be color-coded blue and each cell reference green)

Skills are structured folders — a SKILL.md plus optional scripts and references — encoding a full multi-step workflow. They live in your account's skill library, sync (almost) everywhere Claude runs, and fire either automatically when relevant or on demand via a slash command. Think of these as repeatable processes you can automate (two starter examples: rewriting notes to match your voice, cleaning up call transcripts)

Here's the part that actually costs you time: Instructions are app-specific. Skills are global. The Excel Instructions field and the PowerPoint Instructions field don't talk to each other — set a rule in one, and the other has no idea it exists. And neither talks to the web Profile Preferences field either (claude.ai → your initials → Settings → Profile). If you split your week between web for writing and Excel for modeling, as most StratFin people do, your core standing rules need to live in both places, not one.

[same diagram, "instructions_vs_skills_split"]

A skill you built for writing — a voice file, say — technically counts as available everywhere. It just won't surface inside Excel unless it's Excel-relevant. Relevance still gates the trigger. If you want a finance-specific skill in the Excel sidebar, you upload it there the same way you uploaded it to web; it doesn't show up on its own. You can also build one from inside Excel directly — type /skill-creator in the sidebar, describe the workflow in plain English, and Claude drafts the SKILL.md for you.

Where the “audit” skill actually lives

The skills question gets more tangled once you go looking for a specific one. There isn't a single skill catalog. There are three (womp womp)

Web Skills (claude.ai → Settings → Skills) shows a handful of skills plus anything you've personally uploaded. It was never built to surface plugin-bundled skills individually — search for /audit-xls there and you'll come up empty, not because it's broken, but because that's not where it lives.

Web Plugins (claude.ai → Settings → Plugins) shows a short list of plugins, and each one bundles several skills at once. The Finance plugin, for instance, carries eight. Install the plugin and all eight skills come with it — invisible individually in the Skills tab present the moment you need them (how poetic).

Claude for Excel's pre-loaded skills are a third path entirely, baked into the add-in itself and independent of both catalogs above — /audit-xls, /clean-data-xls, /dcf-model, /comps-analysis. The naming lines up closely enough with the marketplace's own /dcf command that they're likely drawn from the same finance-plugin ecosystem, but they ship inside Excel by default rather than through either web catalog.

There's also a fourth path — third-party marketplaces and Anthropic's own GitHub repo host plugins you can download and upload manually. Thousands are out there. Not all of them are trustworthy, and a self-configured connector especially is worth a second look before you flip it on: it's worth knowing what it actually does and where it sends data, particularly given what these workbooks tend to hold. If you're in a regulated function, expect the approval process to take a while.

The common errors, decoded

Every one of these traces back to the same root cause: assuming a rule set once travels everywhere. It unfortunately doesn't.

A rule set on the web isn't showing up in Excel — because Instructions and Profile Preferences are separate fields. Set it in both, or accept it only applies where you put it.

A skill built for writing doesn't trigger in Excel — global sync doesn't override relevance; an Excel-irrelevant skill won't surface in a spreadsheet context even though it's technically available everywhere.

You went happily looking for "Audit Support" in the web Skills catalog, only to realize it's not there — because it was never a standalone skill. It's bundled inside the Finance plugin, so you install the plugin, not the skill.

None of this is really about Excel. It's about a Claude ecosystem where "set once, apply everywhere" sounds like the default, but it isn’t. Instructions are local. Skills are global but gated by relevance. And a skill you're certain exists might just be living one catalog over from where you're looking for it.