# Limitguard

> Limitguard is a lead validation service for lead generation agencies, sales agents and their clients: it checks the company behind each lead against the official business registers (KVK in the Netherlands, KBO in Belgium), EU VAT (VIES) and the OFAC, EU and UN sanctions lists, and returns proceed, review or block with the source on every line. Developers and AI agents can use the same checks over its HTTP API, MCP server and A2A service, hosted in the EU, paid per call with x402 (USDC) or from an API key's prepaid balance.

## Get Started

- [Introduction](https://docs.limitguard.ai/introduction.md): Every lead checked against the official register.
- [Quickstart](https://docs.limitguard.ai/quickstart.md): Run your first lead check in under 3 minutes
- [Authentication](https://docs.limitguard.ai/authentication.md): API keys, x402 USDC micropayments, and sandbox mode
- [Sandbox Mode](https://docs.limitguard.ai/sandbox.md): Test the API for free with a sandbox key: no wallet, no payment, mock data

## Core Concepts

- [Pricing](https://docs.limitguard.ai/pricing.md): API prices: USDC per call, or from a prepaid API key balance
- [x402 Protocol](https://docs.limitguard.ai/x402-protocol.md): Pay-per-use USDC micropayments for AI agents, no subscription required
- [Discovery](https://docs.limitguard.ai/discovery.md): Machine-readable discovery for AI agents: MCP, A2A, x402, and llms.txt

## Guides

- [Error Handling](https://docs.limitguard.ai/guides/errors.md): Complete error catalog with causes and fixes
- [Rate Limits](https://docs.limitguard.ai/guides/rate-limits.md): Rate limit behavior, tiers, and Retry-After headers
- [Webhooks](https://docs.limitguard.ai/guides/webhooks.md): Get sanctions-list changes that affect you pushed to your server
- [Trust Architecture](https://docs.limitguard.ai/guides/trust-architecture.md): Zero-access model, data flow, and security architecture
- [AI Agent Integration](https://docs.limitguard.ai/guides/ai-agent-integration.md): How AI agents discover and use Limitguard: MCP, A2A, and x402
- [Framework Integrations](https://docs.limitguard.ai/guides/frameworks.md): Connect LangChain, CrewAI, or the OpenAI Agents SDK to Limitguard's remote MCP server
- [Pay Per Call](https://docs.limitguard.ai/guides/pay-per-call.md): Call Limitguard with a USDC wallet and a client library: no API key, no subscription

## Post-mortems

- [Downtime log, September 2026](https://docs.limitguard.ai/postmortems/2026-09-downtime-log.md): Planned maintenance on 2026-09-19 and every short downtime shown on the status page since the 2026-09-05 restore
- [Outage post-mortem, 2026-06-19 to 2026-09-05](https://docs.limitguard.ai/postmortems/2026-09-langfuse-event-loop.md): 78 days of 503s from one synchronous call with no timeout on the event loop, why nothing noticed, and what is structurally different now

## API Reference

- [API Reference](https://docs.limitguard.ai/api-reference/introduction.md): Complete reference for every Limitguard API endpoint

## OpenAPI Specs

- [Limitguard API (docs)](https://docs.limitguard.ai/api-reference/openapi.json)
- [Limitguard API (live)](https://api.limitguard.ai/openapi.json)

## Changelog

- [September 24, 2026](https://docs.limitguard.ai/changelog/2026-09-24.md)
- [September 8, 2026](https://docs.limitguard.ai/changelog/2026-09-08.md)
- [September 7, 2026](https://docs.limitguard.ai/changelog/2026-09-07.md)
- [September 5, 2026](https://docs.limitguard.ai/changelog/2026-09-05.md)
- [February 20, 2026](https://docs.limitguard.ai/changelog/2026-02-20.md)

## Optional

- [Limitguard.ai](https://limitguard.ai): Product site
- [API status](https://api.limitguard.ai/health): Live health check
- [Limitguard API llms.txt](https://api.limitguard.ai/llms.txt): The live API's own machine-readable summary (distinct from this docs-site index)