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Guardrails protect your application from malicious input and ensure your outputs meet specific constraints. They are evaluated directly at the gateway layer, requiring no code changes in your app.

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Enforcement modes

When a guardrail matches, it can take one of two actions:
  • Block: The gateway immediately halts the request and returns a 400 Bad Request to your application. The upstream provider is never called, saving you money and tokens.
  • Log Only: The request proceeds normally, but the guardrail match is flagged in your Request Logs. This is useful for testing a new rule before enforcing it.

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Scopes

A guardrail can be applied to:
  • Input: Evaluates the prompt sent to the LLM.
  • Output: Evaluates the response coming from the LLM.
  • Both: Evaluates both the prompt and the response.

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Built-in guardrail types

Keyword Blocklist

Blocks requests/responses containing any word from a configurable list (case sensitive or insensitive).

Regex Match

Matches content against a custom regular expression pattern.

Substring Match

Blocks if the text contains a specific exact substring.

Length Constraints

Enforces a minimum and maximum word count or character count.

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Configuring guardrails

1

Open Guardrails

In your workspace, go to the Guardrails page and click New Guardrail.
2

Set the rule

Give it a name, select the type (e.g. word_count), and configure the settings (e.g. max: 500).
3

Set enforcement

Choose whether the rule should apply to Input, Output, or Both, and select Block or Log Only.
Guardrails are evaluated in the order they appear on the page. The first guardrail set to Block that matches will immediately halt evaluation.