Code Execution MCP

Implements the patterns from Anthropic's "Code Execution with MCP" article for efficient AI agent operations.

Core Insight

Instead of loading thousands of tool definitions upfront and passing intermediate results through model context, agents write code that:

Discovers tools on-demand (progressive disclosure)
Processes data in a sandbox (not in context)
Returns only summarized/filtered results

Result: Up to 98.7% token reduction compared to direct tool invocation.

Features

1. Sandboxed Code Execution

Resource limits (30s timeout, 500MB memory)
Restricted builtins (safe subset)
Safe modules (json, re, math, datetime, etc.)
Workspace file utilities

2. Progressive Tool Discovery

Search tools by query without loading definitions
Get summaries first, full definitions on-demand
Organized by category (security, memory, cluster, etc.)

3. PII Tokenization

Auto-detect sensitive data (emails, phones, SSNs, etc.)
Replace with tokens before data reaches model
Restore when needed for tool calls

4. Skills Persistence

Save reusable code snippets
Build compound capabilities over time
Share across sessions

Tools

Tool	Description
`execute_code`	Run Python in secure sandbox
`search_tools`	Progressive tool discovery
`get_tool_definition`	Load full tool details
`save_skill`	Persist reusable code
`load_skill`	Load saved skill
`list_skills`	List all skills
`sanitize_pii`	Tokenize PII in text
`restore_pii`	Restore tokenized PII
`write_workspace_file`	Persist data to workspace
`read_workspace_file`	Read from workspace
`list_workspace_files`	List workspace contents
`get_execution_stats`	Environment statistics

Usage Examples

Efficient Data Processing

# Instead of returning 10,000 rows to context: code = ''' data = json.loads(read_file("large_dataset.json")) filtered = [d for d in data if d['status'] == 'active'] result = { 'total': len(data), 'active': len(filtered), 'sample': filtered[:5] } ''' execute_code(code) # Returns only summary, not full dataset

Progressive Tool Discovery

# Find security tools (minimal tokens) search_tools("vulnerability", category="security", detail_level="summary") # Load full definition only when needed get_tool_definition("web_vuln_scanner", category="security")

Privacy-Preserving Operations

# Sanitize before processing sanitize_pii("Contact john@example.com at 555-123-4567") # Returns: "Contact [EMAIL_abc123] at [PHONE_def456]" # Restore when needed restore_pii("[EMAIL_abc123]") # Returns: "john@example.com"

Building Skills

# Save a reusable skill save_skill( name="filter_high_risk", code="def filter_high_risk(vulns): return [v for v in vulns if v['severity'] in ['high', 'critical']]", description="Filter vulnerabilities to high/critical only" ) # Use in future code execution code = ''' skill = load_skill("filter_high_risk") exec(skill) vulns = json.loads(read_file("scan_results.json")) result = filter_high_risk(vulns) '''

Installation

cd /mnt/agentic-system/mcp-servers/code-execution-mcp pip install -e .

Configuration

Add to ~/.claude.json:

{ "mcpServers": { "code-execution": { "command": "/mnt/agentic-system/.venv/bin/python3", "args": ["/mnt/agentic-system/mcp-servers/code-execution-mcp/src/code_execution_mcp/server.py"], "disabled": false } } }

Architecture

code-execution-mcp/ ├── workspace/ # Sandboxed file storage ├── skills/ # Persistent skill definitions ├── tools_registry/ # Tool definitions for discovery │ ├── security/ # Security tools │ └── memory/ # Memory tools └── src/ └── code_execution_mcp/ └── server.py # Main MCP server

Security Notes

Code runs with restricted builtins (no open, exec, eval on arbitrary input)
File access limited to workspace directory
Resource limits prevent runaway execution
No network access from sandbox

Code Execution MCP

Code Execution MCP

Core Insight

Features

1. Sandboxed Code Execution

2. Progressive Tool Discovery

3. PII Tokenization

4. Skills Persistence

Tools

Usage Examples

Efficient Data Processing

Progressive Tool Discovery

Privacy-Preserving Operations

Building Skills

Installation

Configuration

Architecture

Security Notes

References

Resources

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