Assay

Official
Rust

The firewall for MCP tool calls. Block unsafe calls, audit every decision, replay anything. Deterministic policy enforcement with replayable evidence bundles.

About Assay MCP Server

The firewall for MCP tool calls. Block unsafe calls, audit every decision, replay anything. Deterministic policy enforcement with replayable evidence bundles.

Features

Tools
Getting Started

1. Install: `cargo install assay-cli` or download from [GitHub Releases](https://github.com/Rul1an/assay/releases) 2. Wrap your MCP server: `assay mcp wrap -- /path/to/your-server` 3. Or use via Official MCP Registry (MCPB): `io.github.Rul1an/assay` 4. Configure policy in `assay.yaml` (paths, CIDRs, tool allow/deny)

Tools (3)
Functions this server exposes to AI clients

assay_policy_decide

Policy decision for tool calls (allow/deny)

assay_check_args

Validates tool arguments against policy

assay_check_sequence

Validates tool call sequence

Example
# Wrap an MCP server with policy enforcement
assay mcp wrap --policy assay.yaml -- npx -y @modelcontextprotocol/server-filesystem /allowed/path
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Compatible With
Claude Desktop
Cursor
Windsurf
VS Code
Zed
Resources
GitHub RepositoryHomepageDocumentation