PostBridge Agent Plugin

Postal execution layer for AI agents: quote, send, track, and prove physical letters from any agent that supports the Agent Plugins open standard.

PostBridge turns a PDF (or generated document) into a physically mailed letter through print-and-mail providers, with carrier tracking and delivery proof. This plugin gives your AI agent that capability via PostBridge's hosted MCP server plus a set of Agent Skills playbooks.

Built on the Agent Plugins specification v1.0.0 — a portable package format for Agent Skills and MCP servers.

What's inside

Component	Location	Purpose
plugin.json	root	Plugin manifest (name postbridge, v0.1.0)
mcp.json	root	Remote MCP server → https://api.postbridge.ai/mcp (Streamable HTTP)
skills/send-letter	skills/	Quote → confirm → send workflow, with 5-country address rules
skills/track-and-proof	skills/	Track mailed letters, retrieve delivery proof
skills/wallet	skills/	Workspace wallet balance and top-up

MCP tools exposed

list_services, get_quote, send_letter, track_letter, get_proof, get_balance, top_up_wallet, list_letters.

Setup

This repository doubles as a Copilot CLI plugin marketplace — users can register it and install the plugin in one step:

copilot plugin marketplace add PostbridgeAI/postbridge-agent-plugin
copilot plugin install postbridge@postbridge-plugins

Or install directly from the repository / a local path with any Agent Plugins-compatible client.

PostBridge's MCP endpoint is subscription-backed and API-key authenticated. The plugin ships no credentials — your client injects the key.

1. Create a workspace at postbridge.ai.
2. Generate an API & MCP key in Settings → API & MCP (subscription-backed; usage consumes the workspace wallet).
3. Install this plugin in your Agent Plugins-compatible client and configure the Authorization: Bearer <your-key> header / credential for the postbridge MCP server.

Per-client notes:

• Cursor — install the plugin, then add your key as a plugin variable / MCP header under Plugins → Configure.
• GitHub Copilot CLI — copilot plugin install from this repo or a marketplace entry, then set the MCP credential.
• Codex / ChatGPT — connect the MCP server and supply the Bearer key in the auth step.

Safety model

• Spend is explicit. send_letter and top_up_wallet move real money; the skills require explicit user confirmation of address, content, service, and price before any spend.
• Server-side auth is fail-closed. The hosted MCP accepts only a subscription-backed SaaS API & MCP key (no UCAN/browser/x402/legacy keys).
• No secrets in the package. The API key is never stored in plugin.json, mcp.json, env, or headers.
• No fabricated proof. Tracking states and delivery proof are reported only as returned by the carrier.

Address support

The send-letter skill bundles a 5-country address reference (US, CA, FR, GB, DE) distilled from PostBridge's deterministic address parser. For other countries, the agent asks the user to confirm layout rather than guess.

Links

• PostBridge — https://postbridge.ai
• Agent Plugins standard — https://agent-plugins.org
• Model Context Protocol — https://modelcontextprotocol.io
• Agent Skills specification — https://agentskills.io/specification

License

MIT — see LICENSE.