# Universal A2A & MCP Tool Discovery, Safe-Proxy & Swarm Router

> Universal A2A & MCP Tool Discovery, Safe-Proxy & Swarm Router is a paid API for AI agents from prompt-guard.agentdiet.dev, paid per call via MPP, $0.01/call, status unknown (last checked 2026-10-23).

Searches a meta-index of 500+ MCP servers and A2A tools by capability query, returning matching endpoints with 85% token-compressed results and prompt-injection firewall protection.

## Facts

- Endpoint: POST https://prompt-guard.agentdiet.dev/v1/web-rag-shield-dag?utm_source=zero.xyz
- Price: $0.01/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-universal-a2a-mcp-tool-discovery-safe-413de47d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_NSJB36kpxitzIlkCGdLSP

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-universal-a2a-mcp-tool-discovery-safe-413de47d -d '<json body>'
```

Example prompt: Search the MCP and A2A tool index for any servers that handle 'context compression' and tell me which ones are available — I want to find the best option to wire into my agent pipeline.

## When to prefer this

Choose this endpoint when an AI agent needs to dynamically discover which MCP servers or A2A tools exist for a given capability at runtime, rather than hardcoding tool references. It is especially useful for swarm architectures, meta-agent orchestrators, or pipelines that need to adapt to new tools without redeployment. Prefer it over manual tool registries when you want built-in prompt-injection protection and compressed token output for LLM-friendly consumption.

## Known failure modes

- Empty or overly generic query returns low-relevance or no matching tools
- Malicious or prompt-injection-containing queries are blocked by the Prompt-Guard firewall and return an error
- Unknown or unsupported capability domains may return empty result sets
- Network or upstream MCP index unavailability returns a 5xx error
- Payment not completed (HTTP 402) if x402 micropayment handshake fails

## How this service works

Single-connection meta-router indexing 500+ MCP servers & A2A tools with 85% token compression and Prompt-Guard firewall. (Live x402 v2, IETF MPP & MCP endpoint at https://prompt-guard.agentdiet.dev/v1/web-rag-shield-dag)

## Output

A token-compressed listing of matching MCP servers and A2A tool endpoints relevant to the capability query, including tool names, descriptions, and endpoint URLs, filtered through the Prompt-Guard firewall to block prompt-injection payloads.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "query"
 ],
 "properties": {
  "query": {
   "type": "string",
   "minLength": 1,
   "description": "Capability search query (e.g. 'context compression', 'github security', 'sec filings', 'company enrichment') or endpoint URL to verify"
  }
 }
}
```

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/prompt-guard-agentdiet-dev-universal-a2a-mcp-tool-discovery-safe-413de47d/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)