Quick Start

1. Install and initialize

npm install veto-sdk
npx veto init

2. Define a rule

Edit veto/rules/default.yaml:

rules:
  - id: limit-transfers
    name: Limit large transfers
    action: block
    tools:
      - transfer_funds
    conditions:
      - field: arguments.amount
        operator: greater_than
        value: 1000

This rule blocks any call to transfer_funds where the amount exceeds 1000.

3. Wrap your tools

import { Veto } from 'veto-sdk';

// Your existing tools
const myTools = [transferFundsTool, sendEmailTool, readFileTool];

// Initialize Veto (loads config from ./veto)
const veto = await Veto.init();

// Wrap tools with validation
const wrappedTools = veto.wrap(myTools);

// Pass to your agent — the interface is identical
const agent = createAgent({
  tools: wrappedTools,
});

When the agent calls transfer_funds({ amount: 5000 }), Veto intercepts and blocks it. The agent receives a ToolCallDeniedError and can try a different approach.

4. Configure validation mode

Edit veto/veto.config.yaml to choose how validation runs:

version: "1.0"
mode: "strict"

validation:
  mode: "custom"     # "api", "kernel", or "custom"

custom:
  provider: "openai"
  model: "gpt-4o-mini"

rules:
  directory: "./rules"
  recursive: true

Mode	How it works	When to use
`api`	Sends validation requests to the Veto server	Production with dashboard
`custom`	Calls an LLM provider directly	Development, no server needed
`kernel`	Uses a local Ollama model	Offline, air-gapped environments

Next steps

TypeScript SDK — full API reference
Python SDK — full API reference
YAML Rule Format — complete rule syntax
Validation Modes — deep dive into each mode

1. Install and initialize

2. Define a rule

3. Wrap your tools

4. Configure validation mode

Next steps

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