Veto is available for both TypeScript/JavaScript and Python. Choose your preferred language below.
System requirements TypeScript/JavaScript
Python
Node.js : 18.0.0 or higherPackage manager : npm, yarn, or pnpmTypeScript (optional): 5.3.0 or higher
Python : 3.10 or higherpip : Latest version recommended Install the SDK Install the CLI globally for interactive commands: Install the CLI globally: Install the CLI globally: With LLM provider support: # OpenAI pip install veto[openai] # Anthropic pip install veto[anthropic] # Google Gemini pip install veto[gemini] # All providers pip install veto[all]
Initialize your project Run veto init to create the Veto configuration structure in your project:
npm/yarn/pnpm
Python
veto-cli (global)
This command creates the following structure:
project-root/ ├── veto/ │ ├── veto.config.yaml # Main configuration │ ├── rules/ │ │ └── defaults.yaml # Default rules │ └── .env.example # Example environment variables └── .gitignore # Updated with veto/.env
Directory structure explained
veto.config.yaml
Main configuration file. Defines validation mode, logging level, and rule directories. version : "1.0" mode : "strict" logging : level : "info" rules : directory : "./rules" recursive : true
rules/ directory
Contains YAML rule files. You can organize rules by domain (e.g., financial.yaml, devops.yaml, security.yaml). # veto/rules/defaults.yaml version : "1.0" name : default-rules rules : - id : example-rule name : Example Rule action : log description : "Logs all tool calls for audit purposes"
.env.example
Template for environment variables. Copy to .env and add your API keys. # LLM Provider API Keys (for semantic validation) OPENAI_API_KEY = sk-... ANTHROPIC_API_KEY = sk-ant-... GEMINI_API_KEY = ... GOOGLE_API_KEY = ... # Veto Cloud (optional) VETO_API_KEY = veto_... VETO_PROJECT_ID = proj_...
Initialize options You can customize the initialization with flags:
Force overwrite Overwrite existing Veto configuration:
Use a policy pack Start with a built-in policy pack:
veto init --pack finance veto init --pack devops veto init --pack security
Policy packs are pre-configured rule sets for common use cases. You can customize them after initialization.
Specify directory Initialize in a specific directory:
veto init --directory ./packages/my-agent
Verify installation Check that Veto is installed correctly:
Create a test file test-veto.ts: import { Veto } from 'veto-sdk' ; async function test () { const veto = await Veto . init (); console . log ( '✅ Veto initialized successfully!' ); console . log ( veto . getHistoryStats ()); } test (). catch ( console . error );
Run it: npx tsx test-veto.ts # or node --loader ts-node/esm test-veto.ts
Create a test file test_veto.py: import asyncio from veto import Veto async def test (): veto = await Veto.init() print ( '✅ Veto initialized successfully!' ) print (veto.get_history_stats()) if __name__ == "__main__" : asyncio.run(test())
Run it: You should see:
✅ Veto initialized successfully! {'total_calls': 0, 'allowed_calls': 0, 'denied_calls': 0, ...}
CLI commands The Veto CLI provides interactive and headless commands:
Interactive Studio Launch the full-screen terminal UI:
Full-screen terminal UI for managing policies, reviewing decisions, running tests, and monitoring agent activity.
Policy generation Generate policy YAML from natural language:
veto policy generate \ --tool transfer_funds \ --prompt "block transfers over $500 to unverified recipients" \ --save ./veto/rules/financial.yaml
Guard check Test a tool call against your rules:
veto guard check \ --tool transfer_funds \ --args '{"amount": 600, "to_account": "EXT-123"}' \ --json
Output:
{ "decision" : "block" , "rule" : "block-large-transfers" , "reason" : "amount 600 > threshold 500" }
Coverage scan Check which tools have rules:
veto scan # Show coverage report veto scan --fail-uncovered # Exit 1 if any tool is unguarded (CI gate) veto scan --suggest # Include YAML suggestions for uncovered tools
Policy diff Compare policy versions:
veto diff financial.yaml # Compare with git HEAD veto diff --old ./rules-v1 --new ./rules-v2 # Compare two snapshots
See the CLI reference for the complete list of commands and options. Docker installation Run Veto in a containerized environment:
FROM node:20-alpine WORKDIR /app COPY package.json package-lock.json ./ RUN npm install COPY . . # Initialize Veto RUN npx veto init CMD [ "node" , "agent.js" ]
Build and run:
docker build -t my-agent . docker run -e OPENAI_API_KEY= $OPENAI_API_KEY my-agent
Environment variables Veto uses environment variables for configuration:
Variable Description Required OPENAI_API_KEYOpenAI API key for semantic validation No ANTHROPIC_API_KEYAnthropic API key for semantic validation No GEMINI_API_KEY / GOOGLE_API_KEYGoogle Gemini API key No VETO_API_KEYVeto Cloud API key No VETO_PROJECT_IDVeto Cloud project ID No VETO_CONFIG_PATHCustom path to veto.config.yaml No VETO_MODEOverride mode from config (strict / log) No
Never commit API keys to version control. Always use environment variables or a secrets manager.
Update Veto Keep Veto up to date:
npm update veto-sdk npm update -g veto-cli
pip install --upgrade veto
Check your installed version:
npm list veto-sdk veto version
Troubleshooting
Veto.init() throws 'No veto directory found'
Make sure you’ve run veto init in your project root. Veto looks for ./veto/veto.config.yaml relative to your current working directory. You can specify a custom path: const veto = await Veto . init ({ configPath: '/path/to/veto' });
Module not found errors (TypeScript)
Ensure your tsconfig.json has: { "compilerOptions" : { "module" : "ESNext" , "moduleResolution" : "bundler" } }
Veto uses ESM imports. If using Node.js, add "type": "module" to your package.json.
Make sure you’re using Python 3.10 or higher: If you’re using virtual environments, ensure Veto is installed in the active environment:
Check your veto.config.yaml: rules : directory : "./rules" # Path relative to veto/ recursive : true # Scan subdirectories
Verify your rule files are valid YAML: Next steps
Quickstart Build your first guarded agent in 5 minutes
Configuration Deep dive into veto.config.yaml options
Writing rules Learn the rule YAML syntax
Examples Real-world integrations with popular frameworks
