Why isn't the BNBCalc MCP server working? (errors and fixes)
Last reviewed Nov 4, 2026 by Jeremy Werden
Short answer
Most BNBCalc MCP problems come from the key: a missing or misspelled x-bnbcalc-mcp-key header, an API key instead of an MCP key, or a key that was regenerated or deleted. Next come a missing or ended MCP subscription, the daily data limit, and Claude Desktop setups without Node.js. BNBCalc's error messages name the cause.
What do the BNBCalc MCP error messages mean?
| Message | What it means | What to do |
|---|---|---|
| "Missing MCP key. Provide x-bnbcalc-mcp-key header" | The server didn't find your key | Check the header is spelled x-bnbcalc-mcp-key and holds your key. The BNBCalc API's x-bnbcalc-api-key header won't work here. |
| "Invalid MCP key" | The key isn't your account's current MCP key | Make sure it's your MCP key (it starts with mcp_), not a BNBCalc API key. If someone clicked Regenerate key or Delete key, put a new key in your config. |
| "MCP access requires an active BNBCalc MCP subscription" | The account has no MCP subscription | Subscribe in Settings → MCP. |
| "MCP key is suspended or inactive" | The subscription has ended, or a payment failed twice | Subscribe again, or pay the open invoice, and the same key works again. |
| "Daily data limit reached for this API key. It resets at 00:00 UTC." | Your account used up the day's data lookups | Wait until 00:00 UTC. The limit is shared with the BNBCalc API, and lookups that fail still count. |
| "AI request rate limit exceeded" or "Too many AI requests in flight" | Too many requests with AI steps at once | Wait a minute, and run AI comps or AI expense estimates two at a time. |
| "External API request timed out; it may still complete. Do not automatically retry." | The call ran longer than two minutes | Don't retry yet. It may still finish, and bill, so ask the assistant to list your saved analyses first. |
| "BNBCalc could not complete this request; try again later" | Something failed on BNBCalc's side | If you were creating an analysis, check your saved analyses before you try again, since one may have been saved. |
Why isn't the BNBCalc MCP server showing up in Claude, Cursor or VS Code?
A missing tool is a setup problem rather than a key problem, and each app has its own fix:
- Claude Code: run
claude mcp list. Ifbnbcalcisn't there, it may have been added to a different project, so add it again with--scope user. - Claude Desktop: the bridge it uses needs Node.js 18 or newer, so install that first. Then check the JSON in
claude_desktop_config.jsonis valid, with no space after the colon in the header line, and quit and reopen the app completely. - Cursor: restart Cursor after saving
mcp.json, checkbnbcalcis switched on in its MCP settings, and read the MCP Logs output for the reason. - VS Code: run MCP: List Servers, start
bnbcalc, and open its output to see what went wrong.
If your app connects over the older SSE method, it won't work either, because the BNBCalc server only takes POST requests over streamable HTTP.
Why can't I use it on Claude's website or in ChatGPT?
Claude's website and ChatGPT sign in to MCP servers differently from desktop apps. Claude's web and mobile connectors only send a custom header like x-bnbcalc-mcp-key for a limited beta group, and ChatGPT's connectors can't send an API key at all. Until the BNBCalc MCP server supports another way to sign in, use Claude Code, Claude Desktop, Cursor or VS Code.
Why does the assistant keep asking me to approve a price?
BNBCalc's paid MCP tools send back their price before they run. BNBCalc tells your assistant to get your yes, and the assistant then calls the tool again to run it, so a quote on its own never costs anything.
Why did a lookup come back empty?
If BNBCalc can't find enough comparable listings near the address, or a listing or property doesn't exist, the tool says so and the call isn't charged. Try the full street address with the ZIP code, a nearby address, or a different bedroom count. Keep in mind that property details, long-term rent estimates, Section 8 rents, the tax calculator and AI comps only work for US properties.
How do I check what's been charged?
Open Settings → MCP in BNBCalc. The MCP Usage card shows each billing period's successful requests, units used, estimated cost and a Usage by tool table, and your invoices sit just above it. You can also ask your assistant "What's my BNBCalc MCP usage this month?", which is free.
If you think a charge is wrong, or something here doesn't fix it, contact BNBCalc support with the time of the call and the error message you saw.
Frequently asked questions
Why does the BNBCalc MCP server say "Missing MCP key" when I've added my key?
The BNBCalc MCP server only reads the key from a header named x-bnbcalc-mcp-key. If your config uses a different name, such as the BNBCalc API's x-bnbcalc-api-key, the server doesn't see the key at all. Rename the header and restart your app.
What do I do if I lose my BNBCalc MCP key?
BNBCalc only shows an MCP key in full once, so click the Regenerate key button, the circular arrows next to your key in Settings → MCP, to get a new one. The old key stops working right away, so update every app that used it.
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How do I add the BNBCalc MCP server to Claude Code, Claude Desktop, Cursor or VS Code?
Subscribe under Settings → MCP in BNBCalc, create an MCP key, then add https://atlas.bnbcalc.com/mcp to your client with the key in an x-bnbcalc-mcp-key header. Claude Code takes one terminal command, Cursor and VS Code take a few lines of JSON, and Claude Desktop needs a small bridge that runs on Node.js.
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BNBCalc MCP server FAQ: cost, data, privacy and limits
The BNBCalc MCP server is a pay-per-call subscription with no monthly fee: 19 of its 31 tools are free, paid calls run from $0.05 to $0.40, and a Listing Audit uses one credit. It works without a Calculator or Markets plan, sees your tool calls but not your chats, and can't edit analyses or log in to Airbnb.
API, MCP & developers
Is there an Airbnb data MCP server for Claude and Cursor? (BNBCalc MCP)
Yes: the BNBCalc MCP server lets Claude Code, Claude Desktop, Cursor and VS Code estimate a property's Airbnb revenue, pull comparable listings and run full deal analyses on BNBCalc data. Subscribe under Settings → MCP, create an MCP key and add it to your app. There's no monthly fee: paid tools bill per successful call, and most tools are free.
Account & login
How do I contact BNBCalc customer service?
Use the Contact Support form at bnbcalc.com/support, which works signed in or out, or Settings, then Support, inside BNBCalc. Both send your message to the BNBCalc team, and the reply comes by email. You can also email [email protected], ideally from the address you sign in with, so BNBCalc can find your account quickly.
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