# A2A Indirect Prompt-Injection & Jailbreak Firewall

> A2A Indirect Prompt-Injection & Jailbreak Firewall is a paid API for AI agents from prompt-guard.agentdiet.dev, paid per call via MPP, $0.005/call, status unknown (last checked 2026-10-23).

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

## Facts

- Endpoint: POST https://prompt-guard.agentdiet.dev/v1/mcp-injection-firewall?utm_source=zero.xyz
- Price: $0.005/call
- Payment: MPP
- Status: unknown
- Last checked: 2026-10-23
- Activations on Zero: 0
- Provider: prompt-guard.agentdiet.dev
- Website: https://prompt-guard.agentdiet.dev
- Canonical page: https://www.zero.xyz/c/prompt-guard-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-c1885873
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_02OzCPOF1zznIjNRQLL4S

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 prompt-guard-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-c1885873 -d '<json body>'
```

Example prompt: Scan this scraped webpage text for any hidden prompt injections or jailbreak instructions before I pass it into my agent pipeline: [paste the untrusted HTML or text here].

## When to prefer this

Choose this endpoint when your AI agent pipeline ingests untrusted external content — scraped web pages, emails, MCP tool responses, or A2A payloads — and you need to sanitize it before passing it to an LLM. Ideal for agentic workflows where indirect prompt injection is a real attack vector. Prefer this over general-purpose content filters when the specific threat model is adversarial LLM instruction injection rather than spam or hate speech.

## Known failure modes

- Empty or missing 'text' field returns a 400 validation error
- Extremely large payloads may time out or be truncated
- Obfuscated or novel injection techniques may evade detection
- Payment failure via x402 returns 402 Payment Required
- Non-text binary content may not be properly parsed

## 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://prompt-guard.agentdiet.dev/v1/mcp-injection-firewall)

## Output

Returns a JSON object containing the sanitized version of the input text with any detected prompt injection or jailbreak payloads removed or flagged, along with detection signals indicating whether malicious content was found.

## 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/prompt-guard-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-c1885873/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from prompt-guard.agentdiet.dev](https://www.zero.xyz/host/prompt-guard.agentdiet.dev/llms.txt)