# 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 2026-10-21).

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

## Facts

- Endpoint: GET https://prompt-guard.agentdiet.dev/v1/prompt-firewall?utm_source=zero.xyz
- Price: $0.005/call
- Payment: MPP
- Status: unknown
- Last checked: 2026-10-21
- 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-e88d3eca
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_uKV40r7A60Y1aPymRRDcV

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-e88d3eca
```

Example prompt: Before you process this scraped webpage content, run it through the prompt injection firewall to detect and strip any hidden instructions or jailbreak payloads: '<scraped HTML or text goes here>'.

## When to prefer this

Choose this endpoint when your AI agent needs to process untrusted external content — web pages, emails, tool outputs, or A2A/MCP payloads — before incorporating them into its reasoning chain. It is specifically designed for the indirect prompt injection attack vector where malicious instructions are hidden inside content that an agent fetches or receives from external sources. Prefer this over generic content filters when you need LLM-specific injection and jailbreak detection rather than general spam or malware scanning.

## Known failure modes

- Empty or missing 'text' parameter returns a 400 validation error
- Extremely large text payloads may be truncated or rejected
- Highly obfuscated injections using novel encoding may evade detection
- Payment failure via x402 results in 402 Payment Required before scan is performed
- Service unavailability returns 5xx error with no sanitized output

## 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/prompt-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 metadata 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-e88d3eca/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)