# 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 a meta-index of 500+ MCP servers and A2A tools by capability query and returns compressed, firewall-screened results via a single connection.

## Facts

- Endpoint: GET https://prompt-guard.agentdiet.dev/v1/agent-tool-marketplace?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-2d2299d3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FUkyXgDeXoAGGIpast8DI

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-2d2299d3
```

Example prompt: Search the MCP and A2A tool marketplace for servers that handle 'SEC filings' — I want to find a tool I can route that task through.

## When to prefer this

Use this endpoint when an agent needs to dynamically discover which MCP server or A2A tool to delegate a subtask to, especially when the tool ecosystem is large and unknown. Prefer it over hardcoding tool URLs, over narrow single-provider directories, or when token budget is tight (85% compression). Best suited for swarm orchestration, meta-routing, and capability-gap detection at runtime.

## Known failure modes

- Empty query string returns validation error
- No tools found matching niche query returns empty result set
- Prompt-Guard firewall blocks potentially unsafe queries
- Payment required (HTTP 402) if x402 payment header is missing or invalid
- Endpoint URL verification query returns compliance status or error if URL is unreachable

## 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/agent-tool-marketplace)

## Output

Returns a compressed list of matching MCP servers and A2A tool entries (from a 500+ item index) relevant to the capability query, filtered through the Prompt-Guard firewall for safety, with token-compressed metadata.

## 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-2d2299d3/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)