Open-source structural hallucination checker for AI agent pipelines

What it does

A structural hallucination checker specifically designed for AI agent pipelines. Unlike truth checking, this tool focuses on catching structural failures that break downstream tools.

Problem it solves

Most agent issues aren't factual errors but structural problems like:

• The model inventing a field in a JSON tool response
• Citing a source that wasn't in the retrieved set
• Prompt injection hidden inside retrieved content
• Claiming a tool returned something it didn't

Four suppressors

The tool includes four suppressors built in Claude Code that run as a single step before agent output reaches users:

• grounding_enforcer - checks whether model output is actually supported by the sources you passed in
• prompt_suppressor - catches injection attempts in retrieved content and tool results
• json_suppressor - validates structured tool responses against expected schemas
• tool_response_suppressor - flags when a tool's claimed output doesn't match what it returned

Availability

The tool is available in two formats:

• A REST API
• An MCP server (works with Claude Desktop, Cursor, Windsurf, etc.)

Free tier offers 500 requests/month with no credit card required.

Source and documentation

GitHub repository: https://github.com/steveswain14/mcp-hallucination-suite

API and documentation: https://certifai.dev