MCP vs Claude Skills: Choosing the Right Extension Model

TL;DR: Claude Skills are filesystem-based instructions that Claude reads. MCP servers are external programs that provide tools Claude can call. Skills = "give Claude knowledge," MCP = "give Claude capabilities."

What Are They?

Claude Skills

Skills are modular instruction packages that extend Claude's knowledge and workflows.

Structure:

~/.claude/skills/my-skill/
├── SKILL.md          # Main instructions + metadata
├── REFERENCE.md      # Supplemental information
└── templates/        # Optional resources

How they work:

Claude reads SKILL.md metadata to decide when to use it
If relevant, Claude loads the instructions
Claude follows the instructions to complete your task
Model-invoked: Claude autonomously decides when to use them

Example use cases:

Company-specific workflows
Document formatting guidelines
Team coding standards
Specialized domain knowledge

Model Context Protocol (MCP)

MCP servers are external programs that provide tools Claude can call.

Structure:

~/.config/mcp-servers/my-server/
├── index.ts          # Server implementation
├── package.json      # Dependencies
└── mcp.json          # Metadata

How they work:

MCP server runs as a separate process
Exposes tools via stdio/HTTP
Claude calls tools with parameters
Server executes code and returns results
Real-time execution: Actual program running, not just instructions

Example use cases:

Database queries
API integrations
File system operations
External service access

Key Differences

Feature	Claude Skills	MCP Servers
Type	Instructions/Knowledge	External Programs
Execution	Claude interprets	Server executes code
Language	Markdown	Any (TypeScript, Python, etc.)
State	Stateless	Can maintain state
Dependencies	None	npm/pip packages
Performance	Token-based	Process-based
Security	Prompt injection risk	Sandboxed execution
Sharing	ZIP file upload	Docker container
Cost	Token usage	Server resources

When to Use Each

Use Claude Skills When...

✅ You need to teach Claude about your workflows
✅ You want to share company knowledge
✅ You need consistent formatting/style
✅ The task requires Claude's reasoning
✅ You don't need external tools/APIs

Example: "Create a skill that teaches Claude how to write our company's technical documentation following our style guide."

Use MCP Servers When...

✅ You need to query databases
✅ You need to call external APIs
✅ You need file system access
✅ You need parallel execution
✅ You need stateful operations
✅ You need reusable tools across projects

Example: "Create an MCP server that connects to our Postgres database and provides tools for querying customer data."

Architecture Comparison

Claude Skills Architecture

User Request → Claude reads SKILL.md → Claude follows instructions
                    ↓
              Token usage increases
              Claude interprets everything

MCP Architecture

User Request → Claude calls MCP tool → Server executes → Returns result
                    ↓                       ↓
              Minimal tokens         Real code execution
              Claude just handles I/O

Hybrid Approach: The Best of Both

You can (and should!) use both:

Skills: For domain knowledge and workflows
MCP: For tool execution and integrations

Example workflow:

Skill teaches Claude about your company's email response style
MCP server provides tools to query Outlook database
Claude combines both: Reads emails via MCP, writes responses using Skill guidelines

Real-World Example: The Sly Professor Server

I built a unified MCP server that demonstrates the power of MCP:

Tools provided:

get_flagged_emails - Query Outlook.sqlite database
email_to_article - Convert emails to knowledge articles
morning_review - Parallel execution of 3 checks (HIL + emails + tasks)
create_article - Generate vault articles with frontmatter
route_context - Smart routing based on keywords

Why MCP instead of Skills?

Database access: Skills can't query SQLite directly
Parallel execution: Promise.all() runs 3 checks simultaneously (4.3x faster!)
File system: Creating articles with proper permissions
Reusability: Same tools work in OpenCode, Claude Code, Cursor, etc.

Performance comparison:

Sequential Python scripts: 13 seconds
MCP parallel execution:    3 seconds  (4.3x faster!)

Migration Path

Start with Skills → Test workflows → Extract to MCP when you need:

External integrations
Performance optimization
Cross-project reusability
Stateful operations

Security Considerations

Claude Skills Risks

Prompt injection: Malicious skills can manipulate Claude
No sandboxing: Skills run in Claude's context
Package installation: Skills can install npm/pip packages

Mitigation: Review skill content before installation

MCP Server Risks

Code execution: Servers run arbitrary code
Network access: Can make external API calls
File system access: Can read/write files

Mitigation:

Review server code
Use Docker containers
Apply principle of least privilege
Audit tool calls

Recommended Stack

For Personal Productivity:

Skills: Company/team workflows, writing style, coding standards
MCP: Database access, email workflows, morning review dashboards

For Development:

Skills: Framework documentation, API patterns, testing guidelines
MCP: Git operations, package management, deployment tools

For Teams:

Skills: Onboarding guides, compliance requirements, brand guidelines
MCP: Shared tooling, CI/CD integration, analytics dashboards

Getting Started

Creating Your First Skill

bash
mkdir -p ~/.claude/skills/my-skill
cat > ~/.claude/skills/my-skill/SKILL.md << 'EOF'
---
name: My First Skill
description: Teach Claude about my workflow
---

# Instructions

When the user asks about [specific task]:
1. [Step 1]
2. [Step 2]
3. [Step 3]
EOF

Creating Your First MCP Server

bash
mkdir -p ~/.config/mcp-servers/my-server
cd ~/.config/mcp-servers/my-server
bun init -y
bun add @modelcontextprotocol/sdk

# Create index.ts with your tools
# See: https://github.com/anthropics/anthropic-quickstarts

Resources

Claude Skills:

MCP Servers:

Conclusion

Skills and MCP serve different purposes and complement each other perfectly:

Skills = Knowledge injection (teach Claude about your domain)
MCP = Capability injection (give Claude programmatic tools)

For maximum productivity, use both: Skills for context, MCP for execution.

The future is hybrid: Skills provide domain expertise while MCP servers handle the heavy lifting of tool execution, API calls, and data access.

Related Articles:

Building Your First MCP Server with TypeScript
ARF - Agents Router Framework for Hierarchical Context Management
Advanced Tool Use Patterns with Claude