Claude Desktop Extensions (DXT/MCP) - AI-Optimized Technical Reference

Core Problem

Claude Desktop without extensions is a $20/month chat application with no file system access, database connectivity, or tool integration. Users resort to manual screenshot uploads and copy-paste workflows.

Critical Success Factors

Extension Categories by Reliability

Tier 1 (Works Most of Time):

• File System extensions - Save most time, occasional permission issues
• PostgreSQL extensions - Connect on first try typically
• GitHub extensions - Stable for repo operations

Tier 2 (Hit or Miss):

• MySQL extensions - Require specific user permissions, not standard database accounts
• API integrations - Break with vendor API changes

Tier 3 (Avoid):

• Docker extensions - Crash with >3 services in compose files
• Memory extensions - Lose data on Claude Desktop updates (every 2 weeks)
• MongoDB extensions - Often abandoned, setup-specific failures

Installation Methods by Success Rate

Method	Success Rate	Failure Modes	Solution
Built-in Directory	80%	"Installation failed" with no details	Restart Claude Desktop, sometimes 3x required
Drag-and-Drop .mcpb	70%	Corrupted files, wrong downloads	Download from GitHub releases, not source ZIP
URL Installation	30%	Network timeouts, fetch errors	Download manually and drag

Critical Configuration Requirements

File System Access

• Never grant home directory access - Exposes SSH keys, browser passwords
• Use specific project folders only (~/Projects)
• macOS requirement: Full Disk Access in System Preferences after Node updates

API Key Setup Failure Pattern

1. Extension requests API key without specifying required scopes
2. User creates key with basic permissions
3. Extension fails with "unauthorized" error
4. User must research extension name + "API permissions" to find requirements
5. Recreate key with expanded permissions

Performance Breaking Points

• Database extensions: >500MB RAM usage indicates malfunction
• UI threshold: >1000 spans breaks debugging interface for distributed transactions
• Extension conflicts: Multiple file system extensions cause system instability

Security Reality

Extension Permissions

• Extensions run in separate processes but have full access to granted permissions
• API keys stored in OS keychain (secure) but extension file access can compromise keychain dumps
• Network access allows arbitrary data transmission to external servers

Trust Levels

• Built-in Directory: Tested by humans, auto-updates
• GitHub Projects: Check last commit date - abandon if >3 months old
• Company Extensions: Postman reliable, most others are employee side projects
• Enterprise: IT departments typically whitelist 3 extensions nobody uses

Troubleshooting Decision Tree

Extension Won't Install

1. "Installation failed" → Restart Claude Desktop
2. Drag-and-drop silent failure → Wrong file type (.mcpb vs source ZIP)
3. Windows Defender block → Add Claude to exceptions
4. macOS compatibility → Check System Preferences → Security & Privacy

Extension Installs But Non-Functional

1. Check logs: Settings → Extensions → [Extension] → Logs
2. API key issues: Remove and re-add (most common cause)
3. File path problems: Extensions default to non-existent paths like /Users/Developer/Projects
4. Permission escalation: macOS may require Full Disk Access post-update

Performance Degradation

1. RAM monitoring: >500MB per extension indicates malfunction
2. Extension conflicts: Disable file system extensions one by one
3. Nuclear option: Uninstall all extensions and reinstall (corrupted extension database)

Resource Requirements

Time Investment

• Initial setup: 2-4 hours including API key configuration and permission debugging
• Per-machine setup: No sync between computers, full reconfiguration required
• Maintenance: Extensions break with Claude updates every 2 weeks

Technical Prerequisites

• Development skills: TypeScript knowledge required for custom extensions
• System administration: Understanding of OS permissions, keychain management
• API management: Multiple service API keys with varying permission requirements

Critical Warnings

What Official Documentation Doesn't Mention

• Extensions hardcode version checks, break with every Claude update
• File system extensions conflict with each other when multiple installed
• .mcpb and .dxt files are identical (marketing rename)
• GitHub extensions don't auto-update, require manual monitoring

Failure Scenarios

• Claude 0.6.8 update: Corrupted extension folders, lost all configurations
• API changes: Slack extension permanently broken after September API changes
• Abandonment: Most GitHub projects are weekend hackathons, never maintained
• Enterprise deployment: Security review process makes extensions practically unusable

Breaking Points

• Restart requirement: Constant Claude Desktop restarts needed for extension loading
• Version compatibility: Extensions often incompatible with latest Claude versions
• Data loss: Uninstalling Claude removes all configurations permanently

Implementation Strategy

Recommended Extension Stack

1. File System extension (Anthropic official) - Core functionality
2. PostgreSQL extension (if database work) - Most reliable database option
3. GitHub extension (Anthropic official) - Repository integration
4. Avoid everything else until specific need proven

Configuration Backup

• Copy ~/Library/Application Support/Claude/ (Mac) or %APPDATA%\Claude\ (Windows)
• Document API keys and settings in external file
• Extension settings stored in multiple locations, some will be missed

Risk Mitigation

• Use separate computer for sensitive work
• Monitor network requests in extension logs
• Limit file access to non-sensitive project directories
• Maintain documentation of working configurations

Alternatives Assessment

When Extensions Aren't Worth It

• Enterprise environments: Security review overhead exceeds productivity gains
• Sensitive data work: Risk of data exfiltration through extension network access
• Unstable workflows: Constant breakage disrupts development flow
• Simple use cases: Manual copy-paste may be more reliable than broken extensions

Extension-Free Workflows

• Use web Claude for basic queries
• Manual file uploads for code review
• Screenshot-based debugging for visual issues
• Copy-paste for database queries and results