AgentSign is an open-source zero trust engine for AI agents. Every agent gets a cryptographic passport -- a self-contained signed JSON that proves identity and works offline. Before any MCP tool access, agents present their passport. AgentSign checks identity, trust score, and pipeline stage, returning ALLOW or DENY. Features: identity pipeline, execution chains, trust scoring (0-100), swarm revocation, HSM support. Self-hosted, on-prem, zero runtime deps. npm install agentsign. MIT licensed.