Agent Skills: The “Plugins” Moment for Everyday AI

There’s a specific kind of disappointment you only get after asking an LLM to “create an Excel report” and receiving… a beautifully formatted description of a spreadsheet that does not exist.

It’s not the model’s fault. LLMs are great at language. They’re not inherently great at deterministic, file-producing, structure-preserving operations. That’s where Agent Skills come in: Anthropic’s answer (announced October 16, 2025) to the question: “How do we give AI real capabilities without turning every user into a developer?”

If MCP is a highway system for AI tooling, Agent Skills are the roundabouts and on-ramps built right into Claude—fast, local, and predictable.

1) What Exactly Is an Agent Skill?

An Agent Skill is a packaged capability Claude can use when it recognises the situation.

A Skill typically includes:

Think: “a tiny, reusable workflow module” rather than “yet another prompt”.

Anthropic’s docs describe Skills as organised folders of instructions, scripts, and resources, including pre-built Skills for common document work (PowerPoint, Excel, Word, PDF), plus custom Skills you can write yourself.

2) Why This Is A Big Deal: Progressive Disclosure (AKA, Don’t Stuff the Context Window)

The clever part isn’t “Claude can run scripts”—lots of systems can do that.

The clever part is how little Claude loads until it needs to.

Claude Code docs describe a three-phase flow:

  1. Startup: load only each Skill’s name + description (keeps startup fast)
  2. Activation: when relevant, Claude asks to use the Skill and you confirm before full instructions load
  3. Execution: load resources and run in the execution environment

In practice, that means:

This is the opposite of the “mega system prompt” era.

3) What Skills Are Great At (And Why LLMs Struggle Without Them)

Problem A: “I need a real file, not a bedtime story about a file.”

Without Skills, the model often produces representations of artefacts—tables in Markdown, pseudo-Excel, fake download links.

With Skills, Claude can actually generate the artefact (e.g., .xlsx, .pptx, .docx) and hand it back.

Problem B: Domain best practices are annoying to repeat

In real work, the prompt is rarely the hard part. The hard part is the standards:

Skills let you bake these standards once—then reuse them consistently.

Problem C: Determinism matters (especially for structured extraction)

When extracting tables from PDFs or producing spreadsheets, you want repeatable output. Skills push more of the job into deterministic tooling rather than hoping the model “describes it correctly”.

4) Agent Skills vs MCP: It’s Not Redundant, It’s Layering

People see “Skills” and immediately ask: Wait, isn’t that what MCP is for?

Not really.

MCP in one paragraph

Anthropic introduced Model Context Protocol (MCP) in November 2024 as an open standard for building secure, two-way connections between AI tools and external data sources—via MCP clients talking to MCP servers.

In other words: MCP is about connecting to outside systems (databases, file stores, SaaS tools, internal services).

Skills in one paragraph

Agent Skills are about packaging repeatable workflows and execution logic inside Claude’s ecosystem, with progressive loading and sandboxed execution.

A useful mental model

Or: Skills optimise “doing the thing”. MCP optimises “reaching the thing”.

5) The Architecture Patterns You’ll Actually Use

5.1 Skills for document-heavy work (the “office grind” you shouldn’t be doing manually)

Pre-built Skills cover common doc tasks: spreadsheets, slides, PDFs, Word docs.

A realistic workflow:

  1. User: “Turn this quarterly sales CSV into a management-ready workbook with a pivot table and chart.”
  2. Claude uses a spreadsheet Skill to generate a real .xlsx artefact.

5.2 Skills for organisational consistency (the “one team, one way” problem)

A custom Skill can encode your team’s standards:

This matters because humans forget standards. LLMs… forget them even faster unless you enforce them.

5.3 MCP for external systems (the “we need live data” problem)

If you need to:

…that’s MCP territory—especially because MCP is designed as an open protocol for those client/server connections.

6) A Minimal Custom Skill Example (Tweakable, Practical)

Below is a lightweight Skill that turns “messy meeting notes” into a consistent UK-style action log.

SKILL.md

---
name: action-tracking
description: Turn meeting notes into a UK-style action log with owners, dates, and risks. Use when the user pastes notes or uploads minutes.
---
​
# Action Tracking Assistant
​
## When to use
- The user provides meeting notes, minutes, or a transcript
- They want actions, owners, deadlines, and risks in a consistent format
​
## Steps
1. Extract decisions (if any) and action items
2. Assign each action an owner (use names given; otherwise use "TBC")
3. Convert relative dates (e.g. "next Friday") into explicit dates if the date is known; otherwise mark "TBC"
4. Flag dependencies and risks
​
## Output format (must follow exactly)
### Decisions
- ...
​
### Action Log
| ID | Action | Owner | Due date | Status | Risk/Dependency |
|---:|---|---|---|---|---|
| A1 | ... | ... | ... | Not started | ... |

Why this works: the description is written in language users actually type, which improves routing. Anthropic also explicitly recommends paying attention to name and description because Claude uses them to decide whether to trigger a Skill.

7) Safety: The Unsexy Part That Makes Skills Usable

Skills run code and interact with files in an execution environment, so the safety model matters. Claude Code docs frame Skills as folders that Claude can navigate and execute within a constrained environment.

Practical safety rules that hold up in real teams:

8) The Real Limitation: Ecosystem Lock-In (For Now)

Skills are incredibly pragmatic—but they’re also ecosystem-bound:

So the trade-off is clear:

If you’re building internal workflows today, Skills are the “get it done this afternoon” move. If you’re building tooling that must survive model churn, MCP becomes increasingly attractive.

Final Take: Skills Make AI Feel Less Like Chat, More Like Software

The biggest shift here isn’t technical—it’s product-shaped:

Agent Skills push Claude closer to what office software has always promised: less time formatting and moving things around, more time deciding what matters.

And that’s the quiet superpower: when execution gets cheaper, ambition gets bigger.