# A2A Indirect Prompt-Injection & Jailbreak Firewall

> A2A Indirect Prompt-Injection & Jailbreak Firewall is a paid API for AI agents from mcp-security.agentdiet.dev, paid per call via MPP, $0.005/call, status unknown (last checked 2026-10-21).

Scans untrusted text, HTML, emails, MCP responses, or A2A payloads for hidden prompt injections and jailbreak attempts, returning sanitized output.

## Facts

- Endpoint: GET https://mcp-security.agentdiet.dev/v1/llm-guard?utm_source=zero.xyz
- Price: $0.005/call
- Payment: MPP
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Provider: mcp-security.agentdiet.dev
- Website: https://mcp-security.agentdiet.dev
- Canonical page: https://www.zero.xyz/c/mcp-security-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-cc5fa318
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_53SqcDig7rgmzDPVCs5_u

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability mcp-security-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-cc5fa318
```

Example prompt: Before you summarize that webpage content I just fetched, run it through the prompt injection firewall first — I want to make sure there are no hidden instructions embedded in the HTML trying to hijack you.

## When to prefer this

Choose this endpoint when your AI agent pipeline ingests content from untrusted external sources — scraped web pages, emails, third-party API responses, MCP tool outputs, or A2A messages — and you need a lightweight, per-call firewall check before that content reaches your LLM. It is especially valuable in autonomous agent workflows where indirect prompt injection poses a real hijacking risk. At $0.005 per call with fast latency, it suits real-time pipelines where safety checks must not add significant overhead.

## Known failure modes

- Empty or whitespace-only text input returns a validation error
- Extremely long payloads may exceed query parameter length limits for GET requests
- Obfuscated or encoded injections may evade detection if encoding is not decoded prior to scanning
- Payment failure (HTTP 402) if USDC balance is insufficient for the $0.005 per-call fee
- Network timeout if the endpoint is temporarily unavailable

## How this service works

Scans untrusted web pages, emails, MCP responses, or A2A payloads for hidden prompt injections and returns sanitized text. (Live x402 v2, IETF MPP & MCP endpoint at https://mcp-security.agentdiet.dev/v1/llm-guard)

## Output

Returns a JSON object indicating whether the input text contains prompt injection or jailbreak payloads, along with sanitized text stripped of malicious instructions, enabling safe downstream LLM processing.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "text"
 ],
 "properties": {
  "text": {
   "type": "string",
   "minLength": 1,
   "description": "Untrusted text, HTML, or tool output to scan for hidden prompt injection or jailbreak payloads"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mcp-security-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-cc5fa318/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mcp-security.agentdiet.dev](https://www.zero.xyz/host/mcp-security.agentdiet.dev/llms.txt)