Postio — Claude Code MCP server: what it does, how to install
Validates UK street addresses, postal codes, email accounts, and phone numbers via Postio. Useful for checkout verification and contact hygiene.
claude mcp add --env POSTIO_API_KEY=<POSTIO_API_KEY> --env POSTIO_BASE_URL=<POSTIO_BASE_URL> --transport stdio mcp -- npx -y @postio/mcpWhat Postio — UK Address, Postcode, Email & Phone Validation 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.
What it helps with
- 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 for the agent
- Find valid postal addresses along Wimpole Street W1G
- Fetch complete property details for UDPRN 25742215
- Check if the mailbox [email protected] exists and point out typos
How to install Postio — UK Address, Postcode, Email & Phone Validation
Platform CLI
claude mcp add --env POSTIO_API_KEY=<POSTIO_API_KEY> --env POSTIO_BASE_URL=<POSTIO_BASE_URL> --transport stdio mcp -- npx -y @postio/mcpReplace <…> with your own values
Platform CLI
codex mcp add mcp --env POSTIO_API_KEY=<POSTIO_API_KEY> --env POSTIO_BASE_URL=<POSTIO_BASE_URL> -- npx -y @postio/mcpReplace <…> with your own values
Config file
{
"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
Config file
{
"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
Platform CLI
gemini mcp add -e POSTIO_API_KEY=<POSTIO_API_KEY> -e POSTIO_BASE_URL=<POSTIO_BASE_URL> mcp npx -y @postio/mcpReplace <…> with your own values
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Postio — UK Address, Postcode, Email & Phone Validation
How to install Postio in Claude Code?
Run claude mcp add postcode-address-validation -e POSTIO_API_KEY=<POSTIO_API_KEY> -- npx -y @postio/mcp in your terminal.
What does Postio do?
It equips the AI client with tools to query Royal Mail PAF UK addresses, resolve UDPRNs, verify mailboxes over SMTP, and check phone status via HLR.
Can the server run without an API key?
Yes, it launches and advertises its tools without crashing. Individual tool executions will fail until you provide the POSTIO_API_KEY variable.
