Lob

A Model Context Protocol server for the Lob.com API. Lets any MCP-compatible LLM (Claude, etc.) verify addresses and send physical mail — postcards, letters, self-mailers, and printed checks — through Lob.

⚠️ Lob produces real physical mail and charges your account. Mail-piece create tools (lob_postcards_create, lob_letters_create, lob_self_mailers_create, lob_checks_create, lob_*_orders_create) are billable. Develop with a test_… API key. Switch to live_… only when you are ready to ship real mail. Always pass an idempotency_key so retries don't duplicate sends.

Features

• 73 tools across 11 resource groups covering the Lob v1 API surface:
  • Address book (CRUD)
  • US + international address verification (single, bulk, autocomplete, identity validation)
  • Postcards, letters, self-mailers, checks (create, list, retrieve, cancel)
  • Templates and template versions (CRUD)
  • Campaigns and creatives (CRUD — require live-mode key)
  • Buckslips, cards, and their print orders
  • Informed Delivery campaigns (require live-mode key)
  • QR-code analytics
  • Resource proofs (preview before send)
  • Bank accounts (CRUD + micro-deposit verification)
  • Webhook subscriptions (CRUD)
• Idempotency support on every billable create endpoint
• Test/live mode detection from API key prefix, surfaced at startup
• PII redaction — address fields are stripped from error output
• Generic extra parameter on every create/update tool — accepts any Lob parameter not enumerated in the schema, so you're never blocked by SDK lag

Requirements

• Node.js ≥ 18
• A Lob API key — get one free at https://dashboard.lob.com/settings/api-keys

Installation

Run via npx (no install)

npx lob-mcp

Install globally

npm install -g lob-mcp
lob-mcp

Install from source

git clone https://github.com/optimize-overseas/lob-mcp.git
cd lob-mcp
npm install
npm run build
node build/index.js

Configuration

The server is configured entirely through environment variables.

Variable	Required	Description
LOB_API_KEY	Yes	Your Lob API key. Use a test_… key during development; mail-piece tools will not produce real mail in test mode.
LOB_API_VERSION	No	Pin a specific Lob API version via the Lob-Version header (e.g. 2020-02-11). Omit to use your account default.
LOB_BASE_URL	No	Override the Lob API base URL. Defaults to https://api.lob.com/v1.

Use with Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "lob": {
      "command": "npx",
      "args": ["-y", "lob-mcp"],
      "env": {
        "LOB_API_KEY": "test_your_key_here"
      }
    }
  }
}

Restart Claude Desktop. The Lob tools should appear in the tool picker.

Use with Claude Code

claude mcp add lob --env LOB_API_KEY=test_your_key_here -- npx -y lob-mcp

Use with the MCP Inspector

npm run inspector

Then open the URL printed to your terminal. Set LOB_API_KEY in the inspector's environment panel before invoking tools.

Tool reference

All tools are namespaced lob_<resource>_<action>. Annotation hints (readOnlyHint, destructiveHint, idempotentHint, openWorldHint) are set per the MCP spec so hosts can render appropriate confirmation prompts for billable / destructive operations.

Address book

• lob_addresses_create · lob_addresses_list · lob_addresses_get · lob_addresses_delete

Address verification

• lob_us_verifications_create · lob_us_verifications_get
• lob_us_autocompletions_create
• lob_intl_verifications_create
• lob_bulk_us_verifications_create · lob_bulk_intl_verifications_create
• lob_identity_validation

Postcards (billable on create)

• lob_postcards_create · lob_postcards_list · lob_postcards_get · lob_postcards_cancel

Letters (billable on create)

• lob_letters_create · lob_letters_list · lob_letters_get · lob_letters_cancel

Self-mailers (billable on create)

• lob_self_mailers_create · lob_self_mailers_list · lob_self_mailers_get · lob_self_mailers_cancel

Checks (billable on create + draws funds)

• lob_checks_create · lob_checks_list · lob_checks_get · lob_checks_cancel

Templates

• lob_templates_create · lob_templates_list · lob_templates_get · lob_templates_update · lob_templates_delete
• lob_template_versions_create · lob_template_versions_list · lob_template_versions_get · lob_template_versions_update · lob_template_versions_delete

Campaigns + creatives

• lob_campaigns_create · lob_campaigns_list · lob_campaigns_get · lob_campaigns_update · lob_campaigns_delete
• lob_creatives_create · lob_creatives_list · lob_creatives_get · lob_creatives_update · lob_creatives_delete

Buckslips, cards, and print orders (orders are billable)

• lob_buckslips_create · lob_buckslips_list · lob_buckslips_get
• lob_buckslip_orders_create · lob_buckslip_orders_list
• lob_cards_create · lob_cards_list · lob_cards_get
• lob_card_orders_create · lob_card_orders_list

Informed Delivery

• lob_informed_delivery_campaigns_create · lob_informed_delivery_campaigns_list · lob_informed_delivery_campaigns_get

QR codes + resource proofs

• lob_qr_codes_list
• lob_resource_proofs_create · lob_resource_proofs_get · lob_resource_proofs_update

Bank accounts (required to draw checks)

• lob_bank_accounts_create · lob_bank_accounts_list · lob_bank_accounts_get · lob_bank_accounts_delete · lob_bank_accounts_verify

Webhooks

• lob_webhooks_create · lob_webhooks_list · lob_webhooks_get · lob_webhooks_update · lob_webhooks_delete

Safety model

This server enforces three safety practices appropriate for a real-money API:

1. Test/live mode detection. The server inspects your API key prefix at startup and logs the active mode to stderr. A test_… key produces no real mail; a live_… key produces real, billable mail.
2. Idempotency. Every billable create tool exposes an optional idempotency_key parameter. Pass a UUID (or any unique string up to 256 characters) per logical request. Lob will return the original response for any subsequent request reusing the same key, preventing duplicate mail on network retries.
3. PII redaction in errors. Address, name, and contact fields are stripped from any error payload echoed back to the client. The full request body is never logged; only error metadata (status, code, request id, message) is surfaced.

The extra escape hatch

Lob's API has many resource-specific options that aren't worth enumerating in a tool schema (custom envelope IDs, perforation pages, billing groups, marketing flags, etc.). Every create/update tool accepts an optional extra object whose keys are merged verbatim into the request body:

{
  "to": "adr_123…",
  "from": "adr_456…",
  "front": "<html>…</html>",
  "back": "<html>…</html>",
  "extra": {
    "billing_group_id": "bg_…",
    "use_type": "marketing"
  }
}

Refer to https://docs.lob.com/ for the full set of parameters per resource.

Development

npm install
npm run build
npm run typecheck
npm run inspector

The compiled output lives in build/. Source is in src/.

Architecture

src/
├── index.ts            # stdio entry — boots McpServer + LobClient
├── env.ts              # env loading + test/live mode detection
├── lob/
│   ├── client.ts       # fetch-based HTTP client (Basic auth, idempotency, errors)
│   ├── errors.ts       # LobApiError + tool-friendly formatter
│   └── redact.ts       # PII redaction
├── schemas/
│   ├── common.ts       # address, pagination, idempotency, metadata schemas
│   └── mail.ts         # mail-piece-shared schemas
└── tools/
    ├── helpers.ts      # registerTool helper with consistent error mapping
    ├── register.ts     # wires every group into the server
    └── *.ts            # one file per resource group

The HTTP client is intentionally thin — it does not depend on the official lob-typescript-sdk, which keeps the dependency surface small and gives this server tighter control over headers, retries, and PII handling. New Lob endpoints can be added by registering one more tool against the resource group file (or via the extra escape hatch on existing tools).

Limitations

• Multipart file uploads for resources that accept binary PDF/image bytes are supported by the underlying client (asForm: true) but not yet exposed in any tool — the current tools accept HTML strings, URLs, template IDs, and base64 data URIs, which covers the documented Lob content-source forms.
• OAuth is not supported because Lob does not offer it; auth is HTTP Basic with an API key, per Lob's docs.

Contributing

Issues and pull requests welcome at https://github.com/optimize-overseas/lob-mcp.

License

MIT — see LICENSE.

Disclaimer

This project is not affiliated with, endorsed by, or sponsored by Lob.com. "Lob" is a trademark of Lob.com, Inc. Use of the Lob API is subject to Lob's Terms of Service and Acceptable Use Policy.