# 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 2026-10-21).

Searches 500+ indexed MCP servers and A2A tools by capability query and returns compressed, firewall-filtered matches via a single meta-router connection

## Facts

- Endpoint: GET https://prompt-guard.agentdiet.dev/v1/x402-gateway?utm_source=zero.xyz
- Price: $0.01/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-universal-a2a-mcp-tool-discovery-safe-4a941522
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Vh7s-Pespmvf1VNO-lE5i

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-4a941522
```

Example prompt: Search the MCP tool index for servers that can handle 'company enrichment' and show me the top matches with compressed metadata.

## When to prefer this

Choose this endpoint when an AI agent needs to dynamically discover which MCP server or A2A tool to invoke for a given capability, rather than hardcoding a specific tool. It is especially useful in swarm or multi-agent architectures where routing must be decided at runtime. Prefer this over maintaining a static tool registry when the tool landscape is large (500+), when token budget is constrained (85% compression), or when prompt injection safety via the Prompt-Guard firewall is a requirement.

## Known failure modes

- Empty query returns validation error (minLength:1 not met)
- No matching tools found for obscure or misspelled capability queries
- Index staleness may cause recently deprecated MCP servers to appear in results
- Prompt-Guard firewall may block queries it classifies as adversarial or unsafe
- x402 payment failure results in HTTP 402 response blocking the request
- Highly ambiguous queries may return low-relevance matches across unrelated domains

## 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/x402-gateway)

## Output

A list of matching MCP servers or A2A tools relevant to the capability query, returned with 85% token-compressed metadata and filtered through the Prompt-Guard firewall for safety. Results include tool names, descriptions, and routing information sufficient for an agent to select and connect to the appropriate upstream server.

## 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-4a941522/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)