Module: Insika::SchemaGuard

Defined in:
lib/insika/schema_guard.rb

Overview

Checks a tool call's ARGUMENTS against the tool's JSON Schema, at call time. violation returns nil (fine) or ONE message describing what is wrong — the same idiom as EgressGuard, and consumed the same way: DataDefinedTool turns it into { error: … } for the model, so a malformed call is a correctable answer instead of a request that goes out shaped wrong.

Why this exists: the schema declares the contract, but nothing used to hold the model to it. A call carrying ["arroz"] where the schema says [{query, filters}] was interpolated into the body as-is, the backend answered 200, and the wrong results came back with no error anywhere. Validating here closes that loop and names the fix in the message the model reads next.

Scope: the safe subset ToolDefinition already validates (object/array/string/number/integer/boolean + enum + minItems/maxItems). Only what the schema DECLARES is checked; undeclared keys pass (providers add nothing, and additionalProperties is a tool author's business, not ours).

NEVER coerces. The value the model sent is what reaches the request — the guard only decides whether the call may proceed, so turning it on cannot change the bytes of a call that was already correct.

Constant Summary collapse

NUMERIC_RE =

A scalar the schema calls a number/integer/boolean may arrive as its string form ("2", "true") — providers do that, it is lossless, and rejecting it would break working tools for no gain. Structure (object/array) is NEVER lenient.

/\A-?\d+(?:\.\d+)?\z/
INTEGER_RE = 
/\A-?\d+\z/
BOOLEAN_STRINGS = 
%w[true false].freeze
MAX_REPORTED = 
5

Class Method Summary collapse

Class Method Details

.check(value, schema, path) ⇒ Object

-> [String] problems found at/below path.



66
67
68
69
70
71
72
73
74
 
# File 'lib/insika/schema_guard.rb', line 66

def check(value, schema, path)
  return [] unless schema.is_a?(Hash)

  case schema["type"].to_s
  when "object" then check_object(value, schema, path)
  when "array" then check_array(value, schema, path)
  else check_scalar(value, schema, path)
  end
end

.check_array(value, schema, path) ⇒ Object 



92
93
94
95
96
97
 
# File 'lib/insika/schema_guard.rb', line 92

def check_array(value, schema, path)
  return ["#{path}: expected a list, got #{kind(value)}"] unless value.is_a?(Array)

  problems = size_problems(value, schema, path)
  problems + value.each_with_index.flat_map { |item, i| check(item, schema["items"], "#{path}[#{i}]") }
end

.check_object(value, schema, path) ⇒ Object 



76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
 
# File 'lib/insika/schema_guard.rb', line 76

def check_object(value, schema, path)
  return ["#{path}: expected an object, got #{kind(value)}"] unless value.is_a?(Hash)

  props = schema["properties"] || {}
  missing = Array(schema["required"]).map(&:to_s).reject { |k| value.key?(k) }
  problems = missing.map { |k| "#{path}.#{k}: missing (required)" }

  props.each do |pname, pschema|
    child = value[pname.to_s]
    next if child.nil?

    problems.concat(check(child, pschema, "#{path}.#{pname}"))
  end
  problems
end

.check_scalar(value, schema, path) ⇒ Object 



111
112
113
114
115
116
117
118
119
120
 
# File 'lib/insika/schema_guard.rb', line 111

def check_scalar(value, schema, path)
  type = schema["type"].to_s
  return ["#{path}: expected #{type}, got #{kind(value)}"] unless scalar_ok?(value, type)

  enum = schema["enum"]
  return [] unless enum.is_a?(Array) && !enum.empty?
  return [] if enum.map(&:to_s).include?(value.to_s)

  ["#{path}: #{value.to_s.inspect} is not one of #{enum.map(&:to_s).join('/')}"]
end

.kind(value) ⇒ Object

Name the shape the way a model reads it, not the way Ruby does.



135
136
137
138
139
140
141
142
143
144
145
 
# File 'lib/insika/schema_guard.rb', line 135

def kind(value)
  case value
  when Hash then "an object"
  when Array then "a list"
  when String then "a string"
  when Numeric then "a number"
  when true, false then "a boolean"
  when nil then "nothing"
  else value.class.name.downcase
  end
end

.missing_top_level(schema, values) ⇒ Object

Top-level required uses PRESENCE (an empty string is missing), because these values feed {{placeholder}} interpolation — an empty one produces a silently broken URL/body. Nested required uses JSON Schema semantics (key present), where "" can be a legitimate value.



61
62
63
 
# File 'lib/insika/schema_guard.rb', line 61

def missing_top_level(schema, values)
  Array(schema["required"]).map(&:to_s).reject { |n| Insika::Coercion.present?(values[n]) }
end

.scalar_ok?(value, type) ⇒ Boolean

Returns:

  • (Boolean) 


122
123
124
125
126
127
128
129
130
131
132
 
# File 'lib/insika/schema_guard.rb', line 122

def scalar_ok?(value, type)
  return false if value.is_a?(Hash) || value.is_a?(Array)

  case type
  when "string" then true                       # any scalar stringifies losslessly
  when "number" then value.is_a?(Numeric) || NUMERIC_RE.match?(value.to_s)
  when "integer" then value.is_a?(Integer) || INTEGER_RE.match?(value.to_s)
  when "boolean" then [true, false].include?(value) || BOOLEAN_STRINGS.include?(value.to_s)
  else true                                     # unknown type: not ours to police
  end
end

.size_problems(value, schema, path) ⇒ Object

minItems/maxItems are the only cardinality the authors actually write (a search that takes "1 or more pairs"), and an empty list is exactly the call that reads as success and returns nothing.



102
103
104
105
106
107
108
109
 
# File 'lib/insika/schema_guard.rb', line 102

def size_problems(value, schema, path)
  min = schema["minItems"]
  max = schema["maxItems"]
  problems = []
  problems << "#{path}: needs at least #{min} item(s), got #{value.length}" if min.is_a?(Numeric) && value.length < min
  problems << "#{path}: accepts at most #{max} item(s), got #{value.length}" if max.is_a?(Numeric) && value.length > max
  problems
end

.violation(schema, args) ⇒ Object

schema: canonical JSON Schema (ToolDefinition#parameters). args: the model's kwargs (symbol keys). -> nil | String.



37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
# File 'lib/insika/schema_guard.rb', line 37

def violation(schema, args)
  return nil unless schema.is_a?(Hash)

  values = Insika::Coercion.deep_stringify(args || {})
  missing = missing_top_level(schema, values)
  return "missing required parameter(s): #{missing.join(', ')}" unless missing.empty?

  problems = []
  (schema["properties"] || {}).each do |pname, pschema|
    value = values[pname.to_s]
    next if value.nil?

    problems.concat(check(value, pschema, pname.to_s))
    break if problems.length >= MAX_REPORTED
  end
  return nil if problems.empty?

  "invalid arguments: #{problems.first(MAX_REPORTED).join('; ')}"
end