Parameter Constraints

Parameter constraints limit the values passed to operations, preventing cost overruns, security issues, and compliance violations. This reference covers all constraint types.

Basic Structure

Parameter constraints are nested under constraints.parameters:

{
  "constraints": {
    "parameters": {
      "operation-pattern": {
        "parameter_name": constraint_specification
      }
    }
  }
}

Type Validation

Ensure parameters match expected types:

{
  "constraints": {
    "parameters": {
      "llm:openai/chat.completions": {
        "max_tokens": {"type": "integer"},
        "temperature": {"type": "number"},
        "model": {"type": "string"},
        "stream": {"type": "boolean"},
        "messages": {"type": "array"}
      }
    }
  }
}

Type	Description	Examples
integer	Whole numbers	1, 2, 100, -5
number	Integers or floats	1, 1.5, 3.14, -0.5
string	Text values	"gpt-4", "hello"
boolean	True or false	true, false
array	Lists	[1, 2, 3], ["a", "b"]
object	Dictionaries	{"key": "value"}

Numeric Constraints

Control numeric ranges with min,max, or range:

{
  "constraints": {
    "parameters": {
      "llm:openai/chat.completions": {
        "max_tokens": {
          "type": "integer",
          "min": 1,
          "max": 4000
        },
        "temperature": {
          "type": "number",
          "range": [0.0, 2.0]
        }
      },
      "finance:transfer": {
        "amount": {
          "type": "number",
          "min": 0,
          "max": 1000000
        }
      }
    }
  }
}

min

Minimum value (inclusive)

max

Maximum value (inclusive)

range

Array [min, max] (shorthand)

Note: Use either min/max OR range, not both.

String Constraints

Control string values with enumerations, patterns, and length limits:

{
  "constraints": {
    "parameters": {
      "llm:openai/chat.completions": {
        "model": {
          "type": "string",
          "allowed_values": ["gpt-3.5-turbo", "gpt-4"]
        }
      },
      "report:generate": {
        "format": {
          "type": "string",
          "allowed_values": ["PDF", "XLSX", "CSV"]
        },
        "time_period": {
          "type": "string",
          "pattern": "^(Q[1-4]|H[1-2]|FY)\\d{4}$"
        }
      },
      "user:create": {
        "username": {
          "type": "string",
          "min_length": 3,
          "max_length": 32,
          "pattern": "^[a-zA-Z0-9_]+$"
        }
      }
    }
  }
}

Constraint	Description	Use Case
allowed_values	Array of permitted strings	Model selection, format types
pattern	Regex (must match entire string)	Date formats, identifiers
min_length	Minimum string length	Usernames, passwords
max_length	Maximum string length	Prevent injection, buffer overflow

Array Constraints

Control array sizes to prevent resource exhaustion:

{
  "constraints": {
    "parameters": {
      "llm:openai/chat.completions": {
        "messages": {
          "type": "array",
          "min_items": 1,
          "max_items": 100
        }
      },
      "database:batch_insert": {
        "records": {
          "type": "array",
          "max_items": 1000
        }
      }
    }
  }
}

min_items

Minimum array length (ensure at least N items)

max_items

Maximum array length (prevent resource exhaustion)

Shorthand Formats

A list is a shorthand allowlist. Each entry is a wildcard pattern matched against the whole value, so gpt-4* allows gpt-4 and gpt-4o. Use allowed_values for exact matches.

List Shorthand

"model": ["gpt-3.5-turbo", "gpt-4*"]

Exact Values

"model": {"allowed_values": ["gpt-3.5-turbo", "gpt-4"]}

Denied Parameters (Injection Defense)

Block dangerous parameter patterns with denied_parameters:

{
  "constraints": {
    "denied_parameters": {
      "llm:**": {
        "prompt": [
          "*DROP TABLE*",
          "*rm -rf*",
          "*eval(*",
          "*exec(*"
        ]
      },
      "tool:shell/*": {
        "command": [
          "*sudo*",
          "*rm -*",
          "*dd if=*"
        ]
      }
    }
  }
}

Patterns Use Wildcards

• * matches any characters, including spaces, /, :, and line breaks
• Patterns are case-sensitive: *DROP TABLE* ≠ *drop table*
• Use wildcards to match substrings: *DROP TABLE* matches "foo DROP TABLE bar"

Combining Patterns

Wrap a condition in {} when one pattern is too broad on its own:

"denied_parameters": {
  "tool:shell/*": {
    "command": [
      "{params.command MATCHES '*curl*' AND params.command MATCHES '*| sh*'}"
    ]
  }
}

This denies curl https://example.com/install.sh | sh and allows curl https://example.com. The expression may reference any parameter of the call.

How Constraints Merge

When policies inherit, constraints merge using "most restrictive wins":

Company Policy:
    max_tokens: [------------ 0 to 4000 ------------]

BU Analytics:
    max_tokens: [------ 0 to 2000 ------]

User Alice:
    max_tokens: [-- 0 to 500 --]

Final Result:
    max_tokens: [-- 0 to 500 --]  ← Most restrictive wins

Company Policy:
    model: [gpt-3.5-turbo, gpt-4, gpt-4-turbo]

BU Analytics:
    model: [gpt-3.5-turbo, gpt-4]

User Alice:
    model: [gpt-3.5-turbo]

Final Result:
    model: [gpt-3.5-turbo]  ← Intersection

Complete Example

Comprehensive constraints

{
  "constraints": {
    "rate_limit": 50,

    "parameters": {
      "llm:openai/chat.completions": {
        "model": {
          "type": "string",
          "allowed_values": ["gpt-3.5-turbo", "gpt-4"]
        },
        "max_tokens": {
          "type": "integer",
          "min": 1,
          "max": 4000
        },
        "temperature": {
          "type": "number",
          "range": [0.0, 2.0]
        },
        "messages": {
          "type": "array",
          "min_items": 1,
          "max_items": 100
        }
      },
      "tool:database/query": {
        "limit": {"type": "integer", "max": 1000},
        "tables": {
          "allowed_values": ["users", "orders", "products"]
        }
      }
    },

    "denied_parameters": {
      "llm:**": {
        "prompt": ["*DROP*", "*DELETE*", "*sudo*"]
      }
    }
  }
}