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FetchSandbox
FetchSandbox

Posted on Originally published at fetchsandbox.com

Lovable's MCP Form Has a None Option. Don't Pick It.

#lovable #mcp #stripe #webhooks

Lovable will let you add a custom MCP server with No authentication.

That option is a trap for FetchSandbox. The hosted endpoint at https://fetchsandbox.com/mcp/v1 forwards Authorization to the backend. Empty bearer is a 401. The 401's job is to send you to /keys.

Get the key first

Sign in at fetchsandbox.com/keys. Hit Create another key. Copy it once. The list later only shows fsk_… prefixes.

Do not paste it into Lovable chat.

Then the form

Connectors → + → MCP server:

  • Server name: FetchSandbox
  • Server URL: https://fetchsandbox.com/mcp/v1
  • Authentication: Bearer token or API key
  • Token: the secret you just copied

Leave OAuth alone. FetchSandbox does not complete that dance from this form.

Chat connectors stay on your account. They are not in the published app.

Then make it misbehave 

Spin up a Stripe test environment and run a payment through it.
Arm webhook_retries and run checkout again.
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A 200 on the first charge is the easy part. The question is whether the same event id credits twice.

The screenshots, the JWT 401 path, and the "paid but still free" read-back are in the canonical guide.

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