Verify US & international addresses and send physical mail (postcards, letters, checks) via Lob. Hosted by usefulapi — connect from Claude, Cursor, or any MCP client.
Team and Enterprise: an Owner adds the connector for the organization first.
Run this command, then run /mcp in Claude Code to log in:
Add to Cursor or add this to ~/.cursor/mcp.json:
{
"mcpServers": {
"lob": {
"url": "https://lob.usefulapi.io/mcp"
}
}
}Add to VS Code or add this to .vscode/mcp.json:
{
"servers": {
"lob": {
"type": "http",
"url": "https://lob.usefulapi.io/mcp"
}
}
}Other MCP clients (Windsurf, Cline, Zed and more): add the URL as a remote MCP server (Streamable HTTP). The client then opens the login page in your browser. Do not add an Authorization header: see Before you connect.
The login page asks for your Lob API key.
Find it in Lob → Settings → API Keys (dashboard.lob.com). Use a test_ key to avoid real mail/charges. Your key is used only to call the API on your behalf and to derive a private account id; it is never shown to anyone.
Add only the URL. Do not add an Authorization header or an API key to the client config. The server signs you in with OAuth: the login page asks for your Lob API key. If the config has such a header, remove it: some clients then send that header instead of the login token, and every call fails with 401.
Turn on the Lob connector, then ask in plain words. The AI picks the tools.
| Tool | Type | What it does |
|---|---|---|
lob_verify_us_address | read | Verify a US address Validate & standardize a US address, returning deliverability, corrected components, and a confidence score. Pass either a single freeform `address` string OR structured `primary_line`/`city`/`state`/`zip_code`. Non-mutating (no mail sent). Lob API: POST /v1/us_verifications. |
lob_verify_intl_address | read | Verify an international address Validate & standardize a non-US address. `country` (2-letter ISO code) is required. Non-mutating (no mail sent). Lob API: POST /v1/intl_verifications. |
lob_us_zip_lookup | read | Look up a US ZIP code Return the cities and state associated with a US ZIP code. Non-mutating. Lob API: POST /v1/us_zip_lookups. |
lob_us_autocomplete | read | Autocomplete a US address Suggest complete US addresses from a partial primary line — useful for address entry. Non-mutating. Lob API: POST /v1/us_autocompletions. |
lob_list_postcards | read | List postcards List sent/scheduled postcards, newest first. Lob API: GET /v1/postcards. |
lob_get_postcard | read | Get a postcard Retrieve a single postcard by id, including status, PDF url, and expected delivery. Lob API: GET /v1/postcards/{id}. |
lob_list_letters | read | List letters List sent/scheduled letters, newest first. Lob API: GET /v1/letters. |
lob_get_letter | read | Get a letter Retrieve a single letter by id, including status, PDF url, and tracking. Lob API: GET /v1/letters/{id}. |
lob_list_checks | read | List checks List sent/scheduled checks, newest first. Lob API: GET /v1/checks. |
lob_get_check | read | Get a check Retrieve a single check by id, including amount, status, and check number. Lob API: GET /v1/checks/{id}. |
lob_list_self_mailers | read | List self-mailers List sent/scheduled self-mailers, newest first. Lob API: GET /v1/self_mailers. |
lob_list_addresses | read | List saved addresses List saved address records, newest first. Lob API: GET /v1/addresses. |
lob_get_address | read | Get a saved address Retrieve a single saved address record by id. Lob API: GET /v1/addresses/{id}. |
lob_list_templates | read | List templates List saved HTML templates usable as postcard/letter artwork. Lob API: GET /v1/templates. |
lob_create_address | write | Save an address record Create a reusable saved address record (does NOT send any mail). Returns an address id (adr_…) usable as `to`/`from` in mail tools. Lob API: POST /v1/addresses. |
lob_create_postcard | write | Send a postcard (COSTS MONEY) ⚠️ SENDS A REAL POSTCARD and charges your Lob account (use a test_ key to avoid real mail/charges). `to` and `from` accept an existing address id (adr_…) or an inline address object. `front`/`back` accept an HTML string, a hosted asset URL, or a template id (tmpl_…). Cancelable only before `send_date`. Lob API: POST /v1/postcards. |
lob_create_letter | write | Send a letter (COSTS MONEY) ⚠️ SENDS A REAL LETTER and charges your Lob account (use a test_ key to avoid real mail/charges). `to`/`from` accept an address id (adr_…) or inline object. `file` accepts an HTML string, a hosted PDF/URL, or a template id (tmpl_…). `color` is required. Cancelable only before `send_date`. Lob API: POST /v1/letters. |
lob_cancel_postcard | write | Cancel a scheduled postcard Cancel a postcard before its send_date so it is never mailed (and not billed). Fails if the send window has passed. Lob API: DELETE /v1/postcards/{id}. |
lob_usage_status | Usage status (free-tier meter) Report the caller's current free-tier usage this month: calls used, monthly limit, remaining, and whether the cap is reached. Read-only; does not count against the meter. | |
lob_request_feature | Request a missing feature Tell usefulapi that the user needs something the Lob tools cannot do yet (a missing tool, field or filter). Call it only when the user asks for something none of the tools can do, and tell the user that you send the request. Do not call it for errors or for normal requests. Do not include personal data, credentials or customer records. Stored with the product name and the client type (for example Claude or Cursor), without the user's account. At most 5 requests per day. Does not count against the meter. | |
lob_upgrade | Upgrade to Pro (unlimited) Subscribe to the Pro plan for UNLIMITED Lob tool calls (the free tier caps monthly usage). Choose monthly ($9/month) or yearly ($90/year — 2 months free) billing. Returns a Stripe Checkout link to open in your browser; after payment your account upgrades automatically. Does not count against the meter. | |
lob_cancel_subscription | Cancel the Pro subscription Cancel the caller's Lob Pro subscription at the end of the paid period (no refund for the current period; unlimited calls continue until then, then the free tier applies). Requires confirm: true. Run lob_upgrade later to undo the cancel before the period ends. Does not count against the meter. |
| Plan | Price | Limit |
|---|---|---|
| Free | $0 | 100 tool calls / month |
| Pro | $9/mo · $90/yr | Unlimited |
Pro covers this Lob server only. Subscribe with lob_upgrade (it returns a Stripe Checkout link). Cancel any time with lob_cancel_subscription: Pro continues to the end of the paid period, with no refund for the current period, and running lob_upgrade before then undoes the cancel. Or write to [email protected].
No. usefulapi is an independent service. It is not affiliated with or endorsed by Lob. The server calls the Lob API with your own Lob access, so it sees only the data that your account can see.
The login page asks for your Lob API key. See Before you connect for where to find it.
No. Add only the URL. Do not add an Authorization header or an API key to the client config. The server signs you in with OAuth: the login page asks for your Lob API key. If the config has such a header, remove it: some clients then send that header instead of the login token, and every call fails with 401.
The login stores them encrypted in the authorization grant of your connection. The server uses them to call the Lob API for you and to derive a private account id for usage metering. usefulapi does not show them on any page or in any reply. To stop all access, remove the connector and change or delete these credentials in Lob.
Yes, if you approve it. 4 of the 18 Lob tools can create or change data. The other 14 are marked read-only. Most MCP clients ask you to approve a tool call before it runs.
The Free plan gives 100 tool calls / month. Pro costs $9/mo or $90/yr, with unlimited tool calls, for this Lob server only. Run lob_usage_status to see how many calls you used.
Ask the AI to run lob_upgrade: it returns a Stripe Checkout link. To cancel, run lob_cancel_subscription. Pro continues to the end of the paid period.
Tell the AI what you wanted to do. It can send the request with lob_request_feature. We store the text with the server name, the type of AI client and the tool you tried, not with your account, and read every request when we plan new tools. You can send up to 5 requests per day.
Any client that supports remote MCP servers (Streamable HTTP) with OAuth login: Claude (web and desktop), Claude Code, Cursor, VS Code, Windsurf and others.
This is a Model Context Protocol endpoint — meant to be connected from an AI client, not opened in a browser. An invalid_token response at the URL is the auth gate working as designed; clients authenticate automatically.