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Length validators check the size of strings, lists, and other collections.
Length validators support transforms when validating strings. Transforms are applied before measuring length.

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length!

Checks that the value has exactly the specified length. 
generate_code:
  output:
    length!: 6
ParameterTypeDescription
valueintegerExact required length
# Exact code length
generate_pin:
  output:
    length!: 4

# Fixed-length ID
create_id:
  output:
    length!: 36  # UUID length

# Specific list size
get_top_results:
  output:
    length!: 5

​
min_length!

Checks that the value has at least the specified length. 
output:
  min_length!: 10
ParameterTypeDescription
valueintegerMinimum required length
# Ensure substantive response
output:
  min_length!: 50

# Require at least one result
search_products:
  output:
    min_length!: 1

# Validate input length
validate_password:
  input:
    password:
      min_length!: 8

​
max_length!

Checks that the value has at most the specified length. 
output:
  max_length!: 1000
ParameterTypeDescription
valueintegerMaximum allowed length
# Limit response length
output:
  max_length!: 500

# Limit results returned
search_products:
  output:
    max_length!: 10

# Username length limit
validate_username:
  input:
    username:
      max_length!: 32

​
Combining Length Validators

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Length Range

output:
  min_length!: 50
  max_length!: 500

​
With Other Validators

output:
  not_null!: true
  type!: "string"
  min_length!: 10
  max_length!: 1000
  contains!: "result"

​
Common Patterns

​
Response Quality Checks

output:
  not_null!: true
  type!: "string"
  min_length!: 20   # Not too short
  max_length!: 2000 # Not too long

​
Array Size Validation

search_products:
  output:
    type!: "array"
    min_length!: 1
    max_length!: 50

recommend:
  output:
    length!: 3  # Exactly 3 recommendations

​
Code Generation

generate_pin:
  output:
    type!: "string"
    length!: 4
    pattern!: "\\d{4}"

generate_code:
  output:
    type!: "string"
    length!: 6
    pattern!: "[A-Z0-9]{6}"

​
Using Transforms

Transforms are applied before measuring length: 
# Trim whitespace before checking length
output:
  min_length!:
    value: 10
    transform: trim

# Collapse whitespace then check length
output:
  max_length!:
    value: 100
    transform: [trim, collapse_whitespace]

​
Notes on Length Calculation

  • Strings: Length is the number of characters
  • Arrays: Length is the number of items
  • Objects: Length is the number of keys
# String length (characters)
output:  # "Hello" has length 5
  length!: 5

# Array length (items)
items:  # [1, 2, 3] has length 3
  length!: 3

# Object length (keys)
config:  # {"a": 1, "b": 2} has length 2
  length!: 2