Bring Direct Mail
to LangChain
Learn how to connect Lob to LangChain and start using 9 AI agent tools in minutes. Fully managed, enterprise secure, and ready to use without writing a single line of code.
What is the Lob MCP Server?
Connect your Lob account to any AI agent and manage direct mail through natural conversation.
What you can do
- Letter Sending — Create and send letters with PDF or HTML content
- Postcard Campaigns — Send postcards with front/back designs
- Check Printing — Create and mail checks with payment details
- Address Verification — Verify and standardize US addresses
- Template Management — Browse and manage mail templates
- Delivery Tracking — Track mail pieces through the postal system
How it works
1. Subscribe to this server
2. Enter your Lob API Key (test or live)
3. Start sending mail from Claude, Cursor, or any MCP-compatible client
Who is this for?
- Marketing — run direct mail campaigns with postcards and letters
- Finance — automate check printing and mailing
- Operations — verify addresses and track mail delivery
Built-in capabilities (9)
Suggest address completions
Send a physical check
Supports certified mail and custom inserts. Send a physical letter
Supports HTML or PDF for front and back. Send a physical postcard
Track a mail piece
List sent letters
List sent postcards
Verify an international address
Verify a US address
Why LangChain?
LangChain's ecosystem of 500+ components combines seamlessly with Lob through native MCP adapters. Connect 9 tools via Vinkius and use ReAct agents, Plan-and-Execute strategies, or custom agent architectures. with LangSmith tracing giving full visibility into every tool call, latency, and token cost.
- —
The largest ecosystem of integrations, chains, and agents. combine Lob MCP tools with 500+ LangChain components
- —
Agent architecture supports ReAct, Plan-and-Execute, and custom strategies with full MCP tool access at every step
- —
LangSmith tracing gives you complete visibility into tool calls, latencies, and token usage for production debugging
- —
Memory and conversation persistence let agents maintain context across Lob queries for multi-turn workflows
Lob in LangChain
Lob and 3,400+ other MCP servers. One platform. One governance layer.
Teams that connect Lob to LangChain through Vinkius don't need to source, host, or maintain individual MCP servers. Every tool call runs inside a hardened runtime with credential isolation, DLP, and a signed audit chain.
Raw MCP | Vinkius | |
|---|---|---|
| Server catalog | Find and host yourself | 3,400+ managed |
| Infrastructure | Self-hosted | Sandboxed V8 isolates |
| Credential handling | Plaintext in config | Vault + runtime injection |
| Data loss prevention | None | Configurable DLP policies |
| Kill switch | None | Global instant shutdown |
| Financial circuit breakers | None | Per-server limits + alerts |
| Audit trail | None | Ed25519 signed logs |
| SIEM log streaming | None | Splunk, Datadog, Webhook |
| Honeytokens | None | Canary alerts on leak |
| Custom domains | Not applicable | DNS challenge verified |
| GDPR compliance | Manual effort | Automated purge + export |
Why teams choose Vinkius for Lob in LangChain
The Lob MCP Server runs on Vinkius-managed infrastructure inside AWS — a purpose-built runtime with per-request V8 isolates, Ed25519 signed audit chains, and sub-40ms cold starts. All 9 tools execute in hardened sandboxes optimized for native MCP execution.
Your AI agents in LangChain only access the data you authorize, with DLP that blocks sensitive information from ever reaching the model, kill switch for instant shutdown, and up to 60% token savings. Enterprise-grade infrastructure, zero maintenance.
* Every MCP server runs on Vinkius-managed infrastructure inside AWS - a purpose-built runtime with per-request V8 isolates, Ed25519 signed audit chains, and sub-40ms cold starts optimized for native MCP execution. See our infrastructure
How Vinkius secures
Lob for LangChain
Every tool call from LangChain to the Lob MCP Server is protected by DLP redaction, cryptographic audit chains, V8 sandbox isolation, kill switch, and financial circuit breakers.
Frequently asked questions
Can I send letters and postcards through the AI agent?
Yes. Create and send letters with PDF/HTML content and postcards with custom designs. Track delivery through the postal system.
Does Lob use Basic Auth?
Yes. Lob uses HTTP Basic Auth with the API Key as username (no password) against api.lob.com/v1.
Can I verify US addresses?
Yes. Verify and standardize US addresses with CASS certification. Returns deliverability status, corrected addresses, and coordinates.
How does LangChain connect to MCP servers?
Use langchain-mcp-adapters to create an MCP client. LangChain discovers all tools and wraps them as native LangChain tools compatible with any agent type.
Which LangChain agent types work with MCP?
All agent types including ReAct, OpenAI Functions, and custom agents work with MCP tools. The tools appear as standard LangChain tools after the adapter wraps them.
Can I trace MCP tool calls in LangSmith?
Yes. All MCP tool invocations appear as traced steps in LangSmith, showing input parameters, response payloads, latency, and token usage.
MultiServerMCPClient not found
Install: pip install langchain-mcp-adapters