🔍 What This Error Means
A 400 error in Agent Hub means the request your custom prompt sent could not be processed by the system. It is not a problem with your account or with Agent Hub itself. Instead, it usually points to something in the way the custom prompt is written or configured.
This is why playbooks keep working while your custom prompt fails. Playbooks are pre-built and validated by Search Atlas, so their structure, variables, and formatting are already correct. A custom prompt is created from scratch, which means a small formatting or input issue can cause the request to be rejected.
⚙️ Common Causes of the 400 Error
Most 400 errors with custom prompts come from one of the following:
- Prompt is too long: Very long prompts can exceed the allowed input size and be rejected. Prompts that go over the character limit are a confirmed cause of this error, especially when they contain long or detailed instructions.
- Unsupported characters: Pasting from another program can add hidden symbols, smart quotes, or formatting that the system cannot read.
- Empty or missing fields: A required field, such as a target URL or keyword, was left blank.
- Broken variables: A placeholder or variable was edited incorrectly, so the system cannot fill it in.
- Invalid links: A URL in the prompt is misspelled, incomplete, or missing the https:// prefix.
🛠️ How to Fix It
Work through these steps in order. Most customers resolve the error within the first few checks.
- Shorten your prompt: Remove any text that is not essential and keep your prompt within the character limit. Keep instructions clear and direct.
- Retype instead of pasting: If you copied the prompt from a document or email, retype it directly into Agent Hub to strip out hidden formatting.
- Check all required fields: Make sure every field the prompt needs is filled in correctly and nothing is left blank.
- Review your variables: Confirm that any placeholders match the format used in working playbooks. Do not change the surrounding symbols.
- Verify your links: Make sure each URL is complete, correctly spelled, and begins with https://.
- Test with a simple prompt: Enter a short, basic prompt to confirm the error is tied to your original wording and not a wider issue.
💡 Tips to Prevent Future Errors
A few habits will help your custom prompts run smoothly every time:
- Start from a playbook: Use a working playbook as a template, then adjust it gradually to fit your needs.
- Build in small steps: Add one instruction at a time and test as you go, so you can quickly spot what causes a problem.
- Keep prompts focused: Clear, concise prompts are less likely to trigger errors and produce better results.
- Avoid special formatting: Stick to plain text and avoid pasting styled content from other tools.
💬 Still Seeing the Error?
If you have tried these steps and the 400 error continues, our team is ready to help. If you need further assistance, click the chat icon in the bottom-right corner of the platform to start a live chat with a member of our team. Sharing the exact prompt you used will help us resolve the issue faster.