Built-in Skills: Documents, Spreadsheets, Presentations
Earlier in this chapter, you learned how to create custom Skills—encoded expertise that teaches Claude specific procedures. But Cowork also comes with built-in Skills for common document formats. These are pre-installed capabilities that work out of the box.
What Built-in Skills Are
Built-in Skills are domain-specific capabilities Anthropic has developed and optimized:
| Skill | File Types | What It Does |
|---|---|---|
| docx | .docx | Read, create, and edit Word documents |
| xlsx | .xlsx | Read, analyze, and modify spreadsheets |
| pptx | .pptx | Create and edit PowerPoint presentations |
| Extract text and structure from PDFs |
These Skills are pre-installed—you don't need to create or configure them. They're automatically available when working with these file types in Cowork.
The Skills library continues to grow. Beyond the four document-focused Skills detailed in this lesson, Cowork now includes:
- canvas-design — Create and edit visual designs and diagrams directly in Cowork
- skill-creator — Build custom Skills from within Cowork itself (a meta-skill for creating new Skills without leaving the interface)
An open-source community is also building and sharing Skills at github.com/anthropics/skills, which means the Skills ecosystem extends well beyond Anthropic's built-in offerings.
The docx Skill: Word Documents
Capabilities:
- Create new Word documents with proper formatting
- Edit existing documents while preserving structure
- Work with tracked changes
- Maintain styles, headers, footers, and page layouts
- Add tables, lists, and formatting
Example prompt:
"Create a Word document called 'meeting-notes.docx' with:
- Title: 'Q1 Planning Meeting - January 15, 2026'
- Attendees section with placeholder names
- Agenda items: Budget Review, Timeline Discussion, Resource Allocation
- Action items table with columns: Task, Owner, Due Date
- Professional formatting with headers and bullet points"
What Claude does:
- Creates the .docx file
- Adds formatted content with proper document structure
- Applies styles for headings, lists, and tables
- Produces a file you can open directly in Word
Advanced operations:
"Open 'proposal-draft.docx', find all instances of 'Q1 2026' and replace with 'Q2 2026'. Add a tracked changes comment explaining the update. Preserve all existing formatting."
Tracked changes support: When editing existing documents, Claude can use Word's tracked changes feature so you can review modifications before accepting them.
Limitations:
- Complex layouts (newsletters, brochures) may not preserve perfectly
- Macros and VBA are not executed or modified
- Very large documents (>100 pages) may have processing delays
The xlsx Skill: Spreadsheets
Capabilities:
- Read spreadsheet data intelligently
- Analyze data and generate insights
- Add or modify rows and columns
- Create formulas that reference existing data
- Generate charts and visualizations
- Preserve formatting and existing formulas
Example prompt:
"Read 'sales-data.xlsx'. Analyze the sales figures and:
- Calculate total sales by region
- Identify top 5 products by revenue
- Find month-over-month growth rate
- Add a new tab called 'Summary' with this analysis in a clean table
- Create a bar chart showing sales by region"
What Claude does:
- Reads the spreadsheet data
- Analyzes patterns and calculates metrics
- Creates a new worksheet with the summary
- Generates a chart based on the data
- Updates the file while preserving original data
Formula awareness: Claude understands spreadsheet formulas and can:
- Explain what existing formulas do
- Create new formulas using appropriate functions
- Reference cells correctly when adding data
- Avoid breaking formula dependencies
Best practices:
- Always back up spreadsheets before bulk modifications
- Test formula changes on a small sample first
- Ask Claude to explain formulas you don't understand
Limitations:
- Very complex spreadsheets with thousands of formulas may be slow
- Custom functions and add-ins are not executed
- Power Query and Power Pivot operations may not preserve perfectly
The pptx Skill: Presentations
Capabilities:
- Create presentation decks from outlines
- Add and arrange slides
- Format text, shapes, and images
- Apply consistent themes
- Add speaker notes
Example prompt:
"Create a PowerPoint presentation called 'product-update.pptx' with:
- Title slide: 'Q1 Product Roadmap Update'
- Overview slide with key achievements
- 3 feature spotlight slides with bullet points
- Timeline slide showing Q2 plans
- Conclusion slide with next steps
- Use a professional design with consistent colors throughout"
What Claude does:
- Creates the presentation file
- Adds slides with proper layouts
- Formats content consistently
- Applies a theme with unified styling
- Includes speaker notes for key points
Working with existing presentations:
"Open 'deck-template.pptx'. Update the data slide with new figures from 'q1-results.xlsx'. Add two slides at the end summarizing key takeaways. Match the existing design style."
Limitations:
- Complex animations and transitions may not preserve
- Embedded videos and media may need manual re-linking
- Highly custom slide layouts may not replicate perfectly
The pdf Skill: PDF Content
Capabilities:
- Extract text content from PDFs
- Identify document structure (headings, sections)
- Understand tables and data in PDFs
- Work with both text-based and scanned PDFs (OCR)
Example prompt:
"Read 'contract-2024.pdf'. Extract and summarize:
- Key terms and obligations
- Payment schedule and amounts
- Important dates and deadlines
- Any unusual or concerning clauses Organize this into a structured summary document."
What Claude does:
- Extracts text from the PDF
- Identifies document structure and sections
- Organizes key information logically
- Creates a readable summary with proper formatting
PDF limitations:
- Images within PDFs are described, not analyzed visually
- Highly formatted layouts may lose some structure
- Password-protected PDFs cannot be read
- Some PDFs with complex formatting may have extraction errors
When to Use Built-in vs. Custom Skills
Use built-in Skills when:
- Working with standard document formats
- You need format preservation
- The task involves reading/writing Office documents
- You want reliable, tested functionality
Use custom Skills when:
- You have domain-specific procedures
- You need consistent reasoning patterns
- Built-in capabilities don't cover your use case
- You want to encode expertise that applies across document types
Skills within the Plugin architecture: Skills are now one component within Cowork's Plugin system. A Plugin can bundle multiple Skills — both built-in and custom — together with Connectors and slash commands into a complete workflow package. For example, a "Legal Review" Plugin might combine the built-in docx Skill with a custom contract-analysis Skill and a court-filing Connector. See Lesson 29 for how Plugins, Skills, and Connectors fit together.
Cross-App Orchestration
Built-in Skills become most powerful when chained across applications. Cowork can pass context between different document formats in a single workflow:
Example: Excel to PowerPoint pipeline
"Read the Q4 sales data from 'quarterly-results.xlsx'. Identify the top 5 regions by revenue and the 3 fastest-growing product lines. Then create a PowerPoint presentation called 'q4-executive-summary.pptx' with: a title slide, a chart slide showing regional performance (using the xlsx data), a slide highlighting growth trends, and an action items slide. Use the formatting style from 'template.pptx' if it exists."
Claude uses the xlsx Skill to read and analyze the spreadsheet, then the pptx Skill to create the presentation — passing the analysis context between formats without you exporting, reformatting, or copy-pasting anything.
Other cross-app patterns:
| Source → Destination | What Happens |
|---|---|
| PDF → docx | Extract contract terms from PDF, create editable summary in Word |
| xlsx → docx | Analyze spreadsheet data, generate formatted report document |
| Multiple PDFs → xlsx | Extract data from several PDFs, compile into structured spreadsheet |
| docx → pptx | Convert a written brief into presentation slides |
The key insight: individual Skills handle format mechanics, but cross-app orchestration is where Cowork eliminates the manual glue work between applications.
Example combination:
- Built-in docx Skill for Word document creation
- Custom Skill for "legal contract review" reasoning
- Combined: Claude creates a properly formatted document AND applies legal analysis expertise
Capability Matrix
| Task | docx | xlsx | pptx | |
|---|---|---|---|---|
| Read content | ✓ | ✓ | ✓ | ✓ |
| Create new | ✓ | ✓ | ✓ | ✗ |
| Edit existing | ✓ | ✓ | ✓ | ✗ |
| Format preservation | ✓ | ✓ | ✓ | N/A |
| Formulas | N/A | ✓ | N/A | N/A |
| Charts/visuals | Limited | ✓ | Limited | N/A |
| Tracked changes | ✓ | N/A | N/A | N/A |
Best Practices
For documents (docx):
- Use tracked changes when editing important documents
- Describe the desired structure clearly
- Specify formatting requirements explicitly
For spreadsheets (xlsx):
- Always back up before bulk operations
- Ask Claude to explain formulas before applying them
- Test on a small sample when modifying large datasets
For presentations (pptx):
- Provide an outline for better structure
- Specify design requirements (colors, fonts, themes)
- Review generated slides for consistency
For PDFs:
- Understand that extraction may have errors
- Verify important information against the original
- Use PDFs as reference, not as editable source
Try With AI
Design a Cross-App Workflow:
"I work with [describe your document types — e.g., Excel reports, Word proposals, PDF contracts, PowerPoint decks]. Design a workflow where Claude chains two or more built-in Skills together: read data from one format, process it, and output in another. Include the exact prompt I would use and explain which Skills handle which step."
What you're learning: Cross-app orchestration design — understanding how to chain built-in Skills across document formats to eliminate the manual copy-paste-reformat cycle. This is where built-in Skills create the most time savings.
Combine Built-in and Custom Skills for Real Work:
"Pick a task I do that requires both format handling (creating or editing a docx/xlsx/pptx) AND domain-specific reasoning (e.g., financial analysis, legal review, technical documentation standards). Design a workflow that uses a built-in Skill for the format work and describes what a custom Skill would add for the domain reasoning. What would the combined output look like compared to using either alone?"
What you're learning: Skill composition — understanding why format mechanics (built-in) and domain expertise (custom) are separate capabilities that multiply each other's value when combined.
What's Next
You've explored Cowork's interface, workflows, browser integration, connectors, and built-in Skills. The final lesson in this Cowork section brings everything together with a decision framework—helping you choose between Claude Code and Claude Cowork for any given task, and understanding when to use both together.