TOOLS_HOST_UNREACHABLE
Issue
Glean couldn't reach the server it needed, so the request never got a response. You can see this error in two places:
- While a custom tool runs: Glean couldn't connect to the API URL in the tool's definition.
- While connecting a tool: Glean couldn't reach the app's OAuth token URL to finish signing in.
Common causes are a mistyped URL, a host name that doesn't resolve, a server that is down, a Transport Layer Security (TLS) certificate that Glean doesn't trust, or a private server that blocks connections from Glean.
Resolution
Only an admin can fix this error. If you're an end user, send your admin the error code and the request ID from the error message.
If you're an admin:
- Go to Admin console → Platform → Tools and open the tool.
- Check the server URL, or for a connect failure the Token URL, for typos. Open the URL from a browser outside your private network to confirm that it resolves and responds.
- Check that the server presents a valid TLS certificate from a public certificate authority.
- If the server is in a private network or VPC, it must allow connections from Glean, directly or through an allowlisted proxy. Coordinate with your Glean Solutions Engineer or account team to confirm the proxy endpoints and IP ranges to allowlist. See Connect remote MCP servers to Glean.
- Run the tool again, or connect again.
If you see this while setting up a connector in Admin console → Platform → Connectors, check the Token URL and MCP server URL on the connector's setup page, if it has them, then click Connect again. If the setup page asks for neither, wait a few minutes and click Connect again. Contact Glean Support if the error continues.
For additional assistance, contact Glean Support.