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This article covers the most common issues when installing and using the STE MCP.

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Quick diagnosis

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1. Cannot reach the MCP server

Symptom: “The MCP server couldn’t be reached” or a connection failure on first call. Cause: Your network is blocking outbound traffic to mcp.symmetry.com. This is common with corporate VPNs that have split-tunneling misconfigured. Resolution:
  1. Try from a different network (home Wi-Fi or mobile hotspot) to isolate whether the issue is network-specific.
  2. If it works off-VPN but not on, ask your network/IT team to allow traffic to mcp.symmetry.com.

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2. redirect_mismatch or invalid_redirect_uri after sign-in

Symptom: Browser opens, you sign in, but you seeredirect_mismatchorinvalid redirect_uri. Cause: Symmetry’s OAuth allowlist only accepts port 33418 as a redirect target. If your client uses a different port, the auth flow fails. Resolution:
  1. Claude Code: Remove and re-add the MCP with the --callback-port 33418 flag, then restart Claude Code.
  2. Cursor: This is unusual. Cursor uses port 33418 by default. Open Cursor’s Developer Tools → Console and check the actual redirect URL it tried and update.
  3. Gemini CLI: Confirm your settings.json has redirectUri set explicitly (for example, http://localhost:33418/oauth/callback).

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3. Tools not showing up after installation

Symptom: “The ste MCP isn’t available” even though you just added it. Cause: The MCP was registered but the client session has not reloaded it yet. Resolution:
  1. Cursor: Go to Settings → MCP and check that ste has a green dot. If it’s red or yellow, click into it to see the error message.
  2. Claude Code: Run claude mcp list to confirm ste is registered. If it appears in the list but tools aren’t available in your current chat, you forgot to restart. Exit the session (/exit or close the terminal) and start a fresh one.
  3. Gemini CLI: Confirm your settings.json is valid JSON (no trailing commas, all brackets closed) and restart the CLI.
Note: Claude Code only loads MCPs at startup. Any time you add, remove, or change an MCP, you must restart the session.

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4. Token expired / prompted to sign in again

Symptom: “Token expired” or an unexpected browser sign-in prompt mid-session. Cause: The access token lives 60 minutes; the refresh token lives 24 hours. After 24 hours of inactivity, the full sign-in flow repeats. Resolution:
  1. This is normal and expected. Simply complete the sign-in flow in the browser.
  2. The browser tab will close automatically after authentication and your client will resume.
Note: Token lifetime cannot be extended — this is by design for security.

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5. 403 / request blocked error

Symptom: A tool call fails with a 403 “Request blocked” error. Cause: Symmetry’s edge security filter blocked the request. This typically means the request body is over 64 KB, or it contains patterns the filter treats as suspicious (for example, SQL-like strings). Resolution:
  1. Check whether the request body is unusually large. Multi-employee batch calls can hit the limit.
  2. If the request appears well-formed and small, share the failing request with our team and we can help troubleshoot.

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6. Removing or resetting the STE MCP

Use this when: you need to disconnect, reconfigure, or reset the MCP to a clean state. Cursor: Go to Settings → MCP, click the ste entry, and select Remove. Or delete the ste entry from ~/.cursor/mcp.json. Claude Code:
Then restart Claude Code so the change takes effect. Gemini CLI: Remove the ste-mcp block from ~/.gemini/settings.json and restart the CLI.

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Still stuck?

If none of the above resolves your issue:
  • Reach out to our team with a description of the error, the client you’re using, and (if available) the failing request payload and timestamp.
  • For authentication issues, include the full error message shown in the browser or terminal.