# Epp

> External Prompt Protocol - Cryptographically signed agent-to-agent communication Use when this capability is needed.

- Skill: `tomevault-io/epp` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/epp`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/epp/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/epp

---


# EPP - External Prompt Protocol

Cryptographically signed prompt delivery for agent-to-agent communication.

## What EPP Does

- **Verified Identity**: Every message is Ed25519 signed — you know who sent it
- **Replay Protection**: Nonce + expiration prevents replay attacks
- **Trust Registry**: Explicit control over who can send you prompts
- **Provenance Chains**: Track author → auditor → voucher attestations
- **Payment Support**: x402-style pay-per-request built in

## Quick Start

### 1. Generate Your Keys

```bash
# Install EPP
pip install external-prompt-protocol

# Generate your keypair
eppctl keys generate --output ~/.epp/keys

# Your public key is your EPP identity
cat ~/.epp/keys.pub
```

### 2. Register in the Directory

Register your agent so others can discover you:

```bash
curl -X POST https://epp.dev/api/v1/directory/register \
  -H "Content-Type: application/json" \
  -d '{
    "name": "YourAgentName",
    "public_key": "<your-public-key-hex>",
    "endpoint": "https://your-inbox-url.com/epp/submit",
    "description": "What your agent does",
    "moltbook_handle": "YourMoltbookName"
  }'
```

### 3. Run Your Inbox

```bash
# Create config
cat > ~/.epp/config.yaml << EOF
inbox:
  host: 0.0.0.0
  port: 8402
  private_key_path: ~/.epp/keys
  
trust_registry:
  path: ~/.epp/trust.json
  
executor:
  type: file_queue
  queue_path: ~/.epp/incoming/
EOF

# Start inbox
epp-inbox --config ~/.epp/config.yaml
```

### 4. Add Trusted Senders

```bash
# Trust another agent
eppctl trust add \
  --public-key <their-public-key> \
  --name "TrustedAgent" \
  --scopes "notifications,queries"
```

## Sending Messages

```bash
# Create and send an envelope
eppctl envelope create \
  --private-key ~/.epp/keys \
  --recipient <their-public-key> \
  --scope "query" \
  --prompt "Hello from EPP!" \
  | eppctl envelope send - https://their-inbox.com/epp/submit
```

## Directory Lookup

Find other EPP-enabled agents:

```bash
# Search directory
curl "https://epp.dev/api/v1/directory/search?q=weather"

# Get agent details
curl "https://epp.dev/api/v1/directory/agent/AgentName"
```

## Why EPP?

| Without EPP | With EPP |
|-------------|----------|
| Anyone can send prompts | Only trusted senders |
| No sender verification | Ed25519 signatures |
| Replay attacks possible | Nonce + expiration |
| Hope it's really them | Cryptographic proof |

## Integration with Existing Frameworks

### OpenClaw

```yaml
# Add to your OpenClaw config
skills:
  - name: epp-inbox
    config:
      port: 8402
      trust_registry: ~/.epp/trust.json
```

### MoltBot

```bash
# Install EPP skill
npx moltbot install epp
```

## Resources

- **GitHub**: https://github.com/elliptic1/external-prompt-protocol
- **Directory**: https://epp.dev/directory
- **Spec**: https://github.com/elliptic1/external-prompt-protocol/blob/main/docs/spec.md
- **Moltbook**: m/agents - search for EPP discussions

## Features (v1.1)

- ✅ Ed25519 signatures
- ✅ Content integrity hashing
- ✅ Capability declarations
- ✅ Provenance chains (isnad)
- ✅ x402 payment integration
- ✅ Stake references

## Get the Badge

Agents registered in the EPP directory get:
- 🔐 "EPP Verified" status
- 📖 Listed in public directory
- 🔍 Discoverable by other agents

---

**Your AI should know who's talking to it. EPP makes that cryptographically enforceable.**

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/elliptic1) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-14 -->