MCP To Skill

Workflow

Step 1: Get MCP Configuration

• Method A: User pasted configuration in conversation → Use directly
• Method B: User provided configuration file path → Use that path
• If not provided, ask: "Please provide MCP configuration (paste JSON directly or provide file path)"

Supported formats:

• Stdio MCP (npx-based)
• HTTP MCP
• Direct format (without mcpServers wrapper)

Step 2: Generate the Skill

Determine output location:

• Ask for skill name (or extract from config's name field)
• Output directory: ./skills/<skill-name>/

Execute conversion:

# If configuration is in conversation (Method A):
cat > /tmp/mcp-config.json << 'EOF'
<configuration content>
EOF

npx -y mcp-to-skill generate \
  --mcp-config /tmp/mcp-config.json \
  --output-dir ./skills/<skill-name>

# If configuration is a file path (Method B):
npx -y mcp-to-skill generate \
  --mcp-config <configuration file path> \
  --output-dir ./skills/<skill-name>

Generated structure:

./skills/<skill-name>/
├── SKILL.md              # Instructions (~100 tokens)
└── mcp-config.json       # MCP server config

Step 3: Add Script Support (REQUIRED)

The generated skill needs the environment variable handler script:

# Copy the helper script to the generated skill
mkdir -p ./skills/<skill-name>/scripts
cp $(dirname $0)/scripts/exec-with-env.sh ./skills/<skill-name>/scripts/
chmod +x ./skills/<skill-name>/scripts/exec-with-env.sh

Result structure:

./skills/<skill-name>/
├── SKILL.md
├── mcp-config.json
└── scripts/
    └── exec-with-env.sh  # Environment variable handler

Step 4: Fix SKILL.md Execution Instructions (CRITICAL)

The generated SKILL.md contains wrong instructions. You MUST fix them:

❌ REMOVE all instructions like:

npx -y mcp-to-skill exec --config $SKILL_DIR/mcp-config.json --call '{...}'

✅ REPLACE with script-based execution:

$SKILL_DIR/scripts/exec-with-env.sh $SKILL_DIR/mcp-config.json <tool_name> '{"param": "value"}'

Required changes to generated SKILL.md:

1. Add Commands/Usage section showing script usage:

   ## Commands
   
   **Execute tools:**
   ```bash
   $SKILL_DIR/scripts/exec-with-env.sh $SKILL_DIR/mcp-config.json tool_name '{"param": "value"}'
   

   Examples:

   # Example for tool1
   $SKILL_DIR/scripts/exec-with-env.sh $SKILL_DIR/mcp-config.json tool1 '{"query": "hello"}'
   
   # Example for tool2  
   $SKILL_DIR/scripts/exec-with-env.sh $SKILL_DIR/mcp-config.json tool2 '{"input": "test"}'
   

2. Remove any "npx -y mcp-to-skill exec" references

3. Update description to mention environment variable support

4. Add Execution Strategy section (before Usage Pattern or Error Handling):

   ## Execution Strategy
   
   **Important: Execute directly, don't ask beforehand**
   
   When using this skill, **execute commands directly** without asking users to confirm environment variables are set.
   
   - Environment variable status is determined at execution time
   - If execution fails, the error message will clearly indicate missing configuration
   - Only then inform the user what needs to be configured
   - Follow "fail fast" principle to avoid unnecessary interactions
   
   ❌ **Don't do this:**
   - "Please confirm you have set the API_KEY environment variable"
   - "Before executing, please ensure you have configured..."
   
   ✅ **Do this:**
   - Execute the command directly
   - If it fails, inform the user based on the error message
   

Step 5: Test the Skill

Create symlink for testing:

ln -s ../../skills/<skill-name> .agents/skills/<skill-name>

Or copy to global skills directory:

cp -r ./skills/<skill-name> ~/.config/skills/

Scripts

exec-with-env.sh

Universal MCP Skill executor with environment variable support.

Why needed: MCP configs often contain ${VAR} syntax for API keys. The mcp-to-skill tool doesn't resolve these. This script generates a temporary config with resolved values before execution.

Location: scripts/exec-with-env.sh

Usage:

scripts/exec-with-env.sh <mcp-config.json-path> <tool-name> [arguments-json]

Examples:

# Basic usage
scripts/exec-with-env.sh ./my-skill/mcp-config.json web_search \
  '{"query": "hello world"}'

# Config with default values:
# "API_HOST": "${API_HOST:-https://api.example.com}"
scripts/exec-with-env.sh ./mcp-config.json tool_name '{"input": "test"}'

Supported syntax in mcp-config.json:

• $VAR - Direct replacement
• ${VAR} - Braced format
• ${VAR:-default} - With default value

Error handling:

• Exits if env var not set and no default
• Validates generated JSON before execution

Quick Reference

Reference

• Original project: https://github.com/larkinwc/ts-mcp-to-skill