MCP (alpha) instructions for Cursor don't work

[borekb]

Docs: https://tanstack.com/mcp/latest/docs/connecting#cursor

What it produces in Cursor:

[error] Client error for command Redirect URIs must be localhost or HTTPS

---

This is how it looks:

Detailed output:

As text:

2026-01-14 20:58:14.192 [info] Handling CreateClient action
2026-01-14 20:58:14.192 [info] Creating streamableHttp transport
2026-01-14 20:58:14.195 [info] Handling ListOfferings action, server stored: false
2026-01-14 20:58:14.195 [info] Server creation in progress, waiting for completion
2026-01-14 20:58:14.201 [info] Handling GetInstructions action
2026-01-14 20:58:14.201 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:14.201 [info] Handling GetInstructions action
2026-01-14 20:58:14.201 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:14.201 [info] Handling CreateClient action
2026-01-14 20:58:14.201 [info] CreateClient already in progress, waiting for existing creation
2026-01-14 20:58:14.268 [info] Using OAuth scopes: api
2026-01-14 20:58:14.268 [info] Connecting to streamableHttp server
2026-01-14 20:58:14.269 [info] No stored tokens found
2026-01-14 20:58:15.352 [info] No stored client information found
2026-01-14 20:58:15.353 [info] Using redirect URL {"url":"cursor://anysphere.cursor-mcp/oauth/callback"}
2026-01-14 20:58:15.620 [error] Client error for command Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:15.620 [info] Client closed for command
2026-01-14 20:58:15.621 [warning] Error connecting to streamableHttp server, falling back to SSE: Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:15.621 [warning] Error connecting to streamableHttp server, falling back to SSE: Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:15.621 [info] Connecting to SSE server
2026-01-14 20:58:15.623 [info] No stored tokens found
2026-01-14 20:58:15.628 [info] Handling GetInstructions action
2026-01-14 20:58:15.628 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:15.628 [info] Handling GetInstructions action
2026-01-14 20:58:15.628 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:15.628 [info] Handling GetInstructions action
2026-01-14 20:58:15.628 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:15.628 [info] Handling GetInstructions action
2026-01-14 20:58:15.628 [info] Server creation in progress for getInstructions, waiting
2026-01-14 20:58:16.738 [info] No stored client information found
2026-01-14 20:58:16.740 [info] Using redirect URL {"url":"cursor://anysphere.cursor-mcp/oauth/callback"}
2026-01-14 20:58:16.959 [error] Client error for command Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:16.960 [error] Error connecting to SSE server after fallback: Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:16.960 [info] Client closed for command
2026-01-14 20:58:16.961 [warning] Pending server creation failed: Redirect URIs must be localhost or HTTPS
2026-01-14 20:58:16.981 [info] Handling GetInstructions action
2026-01-14 20:58:16.983 [error] No server info found
2026-01-14 20:58:16.983 [info] Handling GetInstructions action
2026-01-14 20:58:16.983 [error] No server info found
2026-01-14 20:58:16.984 [info] Handling GetInstructions action
2026-01-14 20:58:16.984 [error] No server info found
2026-01-14 20:58:16.985 [info] Handling GetInstructions action
2026-01-14 20:58:16.985 [error] No server info found
2026-01-14 20:58:16.985 [info] Handling GetInstructions action
2026-01-14 20:58:16.985 [error] No server info found
2026-01-14 20:58:16.986 [info] Handling GetInstructions action
2026-01-14 20:58:16.986 [error] No server info found
2026-01-14 20:58:16.987 [info] Handling GetInstructions action
2026-01-14 20:58:16.987 [error] No server info found
2026-01-14 20:58:16.987 [info] Handling GetInstructions action
2026-01-14 20:58:16.987 [error] No server info found
2026-01-14 20:58:17.938 [info] Handling ListOfferings action, server stored: false
2026-01-14 20:58:17.938 [info] Server not yet created, returning empty offerings