jamjet-labs/jamjet-policy

What it does

jamjet-policy is an MCP (Model Context Protocol) stdio interceptor that sits between Claude and MCP servers, applying fine-grained policy controls to all tool/function calls. It reads a single YAML policy file to enforce rules like blocking dangerous operations, requiring manual approval, audit logging, and budget constraints before requests reach the actual MCP server.

How to set up

Install the @jamjet/mcpshim package from the jamjet-labs repository. Configure your MCP client to route stdio through the policy interceptor, then define your policies in a YAML file specifying which tools require approval, should be blocked, audited, or have budget limits. The same policy configuration also integrates with Claude Code's PreToolU for consistent governance.

Key features

• YAML-based policy definitions for easy configuration
• Multiple enforcement modes: block, require_approval, audit, and budget_cap
• Works as stdio interceptor between Claude and MCP servers
• Integrated with Claude Code PreToolU for broader coverage
• Cross-platform support (Windows, macOS, Linux)