# Postio — UK Address, Postcode, Email & Phone Validation

Validates UK street addresses, postal codes, email accounts, and phone numbers via Postio. Useful for checkout verification and contact hygiene.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI
- Author: postio-uk
- License: MIT · policy=link-only · description only; the file stays with the author
- Source: https://github.com/postio-uk/postio-integrations/tree/HEAD/packages/mcp
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/mcp/postio-uk-address-postcode-email-phone-validation

## What it does

This stdio server wraps Postio verification endpoints for AI clients. It exposes tools to inspect Royal Mail PAF records, look up UDPRN entries, parse email addresses through live SMTP tests, and query phone lines via HLR lookups. Responses arrive as raw API JSON envelopes containing `meta.requestId`.

Node 20 or newer is mandatory. You must supply `POSTIO_API_KEY` for live lookups. Without this environment variable, the server boots and advertises its schema to the host, but calling any tool triggers an immediate authentication error.

## Requirements
- Needs: Node.js (commands run via npx)
- Environment variables: `POSTIO_API_KEY`, `POSTIO_BASE_URL` — keys and tokens: ask the human for the values, never commit them or put them in shared files.

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add --env POSTIO_API_KEY=<POSTIO_API_KEY> --env POSTIO_BASE_URL=<POSTIO_BASE_URL> --transport stdio mcp -- npx -y @postio/mcp
```
Replace <…> with your own values

### Codex

**Platform CLI**
```bash
codex mcp add mcp --env POSTIO_API_KEY=<POSTIO_API_KEY> --env POSTIO_BASE_URL=<POSTIO_BASE_URL> -- npx -y @postio/mcp
```
Replace <…> with your own values

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "mcp": {
            "command": "npx",
            "args": [
                "-y",
                "@postio/mcp"
            ],
            "env": {
                "POSTIO_API_KEY": "<POSTIO_API_KEY>",
                "POSTIO_BASE_URL": "<POSTIO_BASE_URL>"
            }
        }
    }
}
```
Replace <…> with your own values

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "mcp": {
            "type": "stdio",
            "command": "npx",
            "args": [
                "-y",
                "@postio/mcp"
            ],
            "env": {
                "POSTIO_API_KEY": "<POSTIO_API_KEY>",
                "POSTIO_BASE_URL": "<POSTIO_BASE_URL>"
            }
        }
    }
}
```
Replace <…> with your own values

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add -e POSTIO_API_KEY=<POSTIO_API_KEY> -e POSTIO_BASE_URL=<POSTIO_BASE_URL> mcp npx -y @postio/mcp
```
Replace <…> with your own values

## When to use it
- Resolve UK postal addresses and retrieve matching UDPRN identifiers
- Inspect mailbox deliverability via SMTP and identify domain typos
- Fetch PAF delivery points registered under a specific postal code
- Check cellular carrier and reachability status through live HLR

## Example prompts
- Find valid postal addresses along Wimpole Street W1G
- Fetch complete property details for UDPRN 25742215
- Check if the mailbox test@gnail.com exists and point out typos

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