# 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 output.

## Facts

- Endpoint: POST https://prompt-guard.agentdiet.dev/v1/system-prompt-guard?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-676f3506
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Zm9t-UJ1C28w_EoaULsKX

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-676f3506 -d '<json body>'
```

Example prompt: Before you summarize that webpage I just fetched, run the raw HTML through the prompt-injection firewall to check for any hidden instructions trying to hijack you, and give me the sanitized version to work with.

## When to prefer this

Choose this endpoint when your agent pipeline ingests content from untrusted external sources — scraped web pages, user-submitted emails, third-party API responses, MCP tool outputs, or A2A messages — and you need a dedicated firewall layer before passing that content to an LLM or triggering downstream actions. Prefer it over generic content filters when your threat model specifically includes indirect prompt injection and jailbreak payloads targeting agentic systems.

## Known failure modes

- Empty or missing 'text' field returns a 400 validation error
- Payment not provided or invalid returns HTTP 402 with x402 payment challenge
- Very large payloads may exceed size limits and return a 413 error
- Obfuscated or novel injection techniques may not be detected (false negatives)
- Network timeouts on the remote endpoint return connection errors

## 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/system-prompt-guard)

## Output

Returns a JSON object indicating whether prompt injection or jailbreak content was detected in the input, along with sanitized text safe for downstream LLM or agent 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/prompt-guard-agentdiet-dev-a2a-indirect-prompt-injection-jailbreak-676f3506/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)