HTTP Request Tool in AI Agent Returns 'Invalid URL' When Connecting to TidyCal API

Below is a list of suggestions to troubleshoot the error, based on known issues with URL formatting in n8n’s HTTP Request nodes:

1. Verify the URL Format

Even if the URL works with the standard HTTP Request node, the HTTP Request Tool (used in AI Agent) validates the URL strictly.
• Ensure the URL is complete and includes the protocol (for example, "https://tidycal.com/api/…").
• Check for extra whitespace or hidden characters that might inadvertently be appended.

2. Check for Expression and String Handling

If you’re using an expression to generate the URL, make sure that:
• The expression resolves to a valid string.
• The complete JSON is wrapped correctly if you’re using it in an expression context. For example:

JAVASCRIPTCopied
{{
  "https://tidycal.com/api/..."
}}

This ensures the URL is interpreted as a string.

3. Recreate the Node Manually

Sometimes, nodes that are cloned from a working HTTP Request node may carry over subtle misconfigurations. Try removing the HTTP Request Tool node entirely and re-adding it, then manually paste the valid URL into the URL field.

4. Compare Settings in Both Nodes

Since the standard HTTP Request node works while the tool version does not, compare all settings closely:
• Make sure there aren’t any differences in query parameters or headers that might inadvertently affect URL parsing.
• Validate that any dynamic parts of the URL (if applicable) resolve exactly the same way in both nodes.

5. Check Documentation

As the HTTP Request Tool node is a specialized version intended for use with AI agents, refer to its documentation for any node-specific quirks. According to the docs, it behaves similarly to the standard HTTP Request node, but minor differences in expression handling or parameter validation could lead to issues like this.

If after following these steps the issue persists, it might be helpful to isolate the problem in a simpler workflow or review the node configuration line-by-line to ensure all parameters (especially the URL) are as expected.

By ensuring the URL field contains a perfectly valid URL and that any expressions are correctly formatted, you should be able to resolve the “Invalid URL” error in the HTTP Request Tool node.