How to Use the Lob MCP in Pydantic AI

Q: How do I connect Lob to my Pydantic AI agent?

Install pydantic-ai-slimmcp and initialize an MCPToolset with the Vinkius MCP Server HTTP URL. Pass this toolset into the Agent constructor.

Q: What happens if a check creation payload is malformed?

If the agent passes invalid fields to createcheck, the framework throws a runtime validation error, stopping the transaction before any API call is made.

Type-safe physical mail automation with Lob and Pydantic AI.

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Connect Lob MCP to Pydantic AI

Create your Vinkius account to connect Lob to Pydantic AI and route execution through our secure gateway. The platform manages server hosting, runtime updates, and security layers. Configuration requires no manual server provisioning.

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Setup Lob with Pydantic AI

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Send validated postcards and letters with Pydantic AI

The `create_postcard` tool sends physical postcards using HTML or PDF designs for both sides. Because this runs on Pydantic AI, every parameter is validated against strict schemas before execution. To send formal documents, `create_letter` handles certified mail and custom inserts. If your agent tries to pass a malformed payload, the framework raises a validation error immediately rather than sending bad data to the printing queue over the MCP Server connection.

Verify addresses using this type-safe MCP Server

The `verify_us_address` tool validates domestic addresses to guarantee deliverability. For global operations, `verify_intl_address` parses international address fields to match local postal standards. Your agent can also use `autocomplete_address` to suggest valid address completions during data entry. This keeps your shipping records clean and minimizes processing failures.

Mail checks and track deliveries safely

The `create_check` tool issues and mails physical checks directly to recipients. Pydantic AI validates the check amounts and routing details at runtime to prevent execution errors. You can monitor delivery progress using `get_mail_tracking` for real-time status updates. To review previous jobs, query `list_letters` and `list_postcards` to keep your system in sync.

Setup guide

Set up Lob MCP in Pydantic AI

Prerequisites

Python 3.10+ installed
pydantic-ai-slim[fastmcp] package
Active Vinkius subscription with a valid endpoint token

1

Install Pydantic AI with FastMCP
Run pip install "pydantic-ai-slim[fastmcp]". The FastMCP toolset replaces the deprecated MCPServerHTTP class with full protocol support.
2

Configure the FastMCPToolset
Pass a JSON-style config dict to FastMCPToolset with your Vinkius URL. Replace [YOUR_TOKEN_HERE] with your token from cloud.vinkius.com. Supports Streamable HTTP, SSE, and Stdio transports.
3

Create and run your agent
Pass the toolset to Agent(toolsets=[toolset]) and call agent.run(). Swap openai:gpt-4o for any supported model — Anthropic, Google, Mistral, or Groq.

agent.py

from pydantic_ai import Agent
from pydantic_ai.toolsets.fastmcp import FastMCPToolset

toolset = FastMCPToolset({
    "mcpServers": {
        "lob-alternative-mcp": {
            "url": "https://edge.vinkius.com/[YOUR_TOKEN_HERE]/mcp"
        }
    }
})

agent = Agent(
    "openai:gpt-4o",
    toolsets=[toolset],
    system_prompt="You have access to Lob tools.",
)

result = await agent.run("List recent Lob transactions")
print(result.output)

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Common questions about Lob MCP in Pydantic AI

Install `pydantic-ai-slim[mcp]` and initialize an `MCPToolset` with the Vinkius MCP Server HTTP URL. Pass this toolset into the `Agent` constructor.

Yes. The framework enforces strict type-checking on responses from `verify_us_address`, preventing your agent from handling unparsed address strings.

Yes. The framework is model-agnostic, letting you run your direct mail workflows using OpenAI, Anthropic, Gemini, or local models.

If the agent passes invalid fields to `create_check`, the framework throws a runtime validation error, stopping the transaction before any API call is made.

This MCP Server runs inside a secure, zero-trust V8 isolate. Address data and check details are processed ephemerally, ensuring no personal information remains stored on the host server.

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