diff --git a/CHANGELOG.md b/CHANGELOG.md
index 43f156a8a..00fc0a244 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+## [0.48.0]
+
+### Added
+- Implements the new OpenAI structured output mode for `aiextract` (just provide kwarg `strict=true`). Reference [blog post](https://openai.com/index/introducing-structured-outputs-in-the-api/).
+
 ## [0.47.0]
 
 ### Added
diff --git a/Project.toml b/Project.toml
index 7c3cd6b13..c2ca2ab49 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "PromptingTools"
 uuid = "670122d1-24a8-4d70-bfce-740807c42192"
 authors = ["J S @svilupp and contributors"]
-version = "0.47.0"
+version = "0.48.0"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"
diff --git a/src/extraction.jl b/src/extraction.jl
index bd77aa1f4..0f591fdeb 100644
--- a/src/extraction.jl
+++ b/src/extraction.jl
@@ -75,18 +75,18 @@ function to_json_schema(orig_type; max_description_length::Int = 100)
     return schema
 end
 function to_json_schema(type::Type{<:AbstractString}; max_description_length::Int = 100)
-    Dict("type" => to_json_type(type))
+    Dict{String, Any}("type" => to_json_type(type))
 end
 function to_json_schema(type::Type{T};
         max_description_length::Int = 100) where {T <:
                                                   Union{AbstractSet, Tuple, AbstractArray}}
     element_type = eltype(type)
-    return Dict("type" => "array",
+    return Dict{String, Any}("type" => "array",
         "items" => to_json_schema(remove_null_types(element_type)))
 end
 function to_json_schema(type::Type{<:Enum}; max_description_length::Int = 100)
     enum_options = Base.Enums.namemap(type) |> values .|> string
-    return Dict("type" => "string",
+    return Dict{String, Any}("type" => "string",
         "enum" => enum_options)
 end
 function to_json_schema(type::Type{<:AbstractDict}; max_description_length::Int = 100)
@@ -94,7 +94,9 @@ function to_json_schema(type::Type{<:AbstractDict}; max_description_length::Int
 end
 
 """
-    function_call_signature(datastructtype::Struct; max_description_length::Int = 100)
+    function_call_signature(
+        datastructtype::Type; strict::Union{Nothing, Bool} = nothing,
+        max_description_length::Int = 100)
 
 Extract the argument names, types and docstrings from a struct to create the function call signature in JSON schema.
 
@@ -123,7 +125,8 @@ signature = function_call_signature(MyMeasurement)
 # Dict{String, Any} with 3 entries:
 #   "name"        => "MyMeasurement_extractor"
 #   "parameters"  => Dict{String, Any}("properties"=>Dict{String, Any}("height"=>Dict{String, Any}("type"=>"integer"), "weight"=>Dic…
-#   "description" => "Represents person's age, height, and weight\n"
+#   "description" => "Represents person's age, height, and weight
+"
 ```
 
 You can see that only the field `age` does not allow null values, hence, it's "required".
@@ -161,7 +164,9 @@ msg = aiextract("Extract measurements from the text: I am giraffe", type)
 ```
 That way, you can handle the error gracefully and get a reason why extraction failed.
 """
-function function_call_signature(datastructtype::Type; max_description_length::Int = 100)
+function function_call_signature(
+        datastructtype::Type; strict::Union{Nothing, Bool} = nothing,
+        max_description_length::Int = 100)
     !isstructtype(datastructtype) &&
         error("Only Structs are supported (provided type: $datastructtype")
     ## Standardize the name
@@ -177,9 +182,56 @@ function function_call_signature(datastructtype::Type; max_description_length::I
        schema["parameters"]["description"] == docs
         delete!(schema["parameters"], "description")
     end
+    ## strict mode // see https://platform.openai.com/docs/guides/structured-outputs/supported-schemas
+    if strict == false
+        schema["strict"] = false
+    elseif strict == true
+        schema["strict"] = true
+        if haskey(schema["parameters"], "properties")
+            set_properties_strict!(schema["parameters"])
+        end
+    end
     return schema
 end
 
+"""
+    set_properties_strict!(properties::AbstractDict)
+
+Sets strict mode for the properties of a JSON schema.
+
+Changes:
+- Sets `additionalProperties` to `false`.
+- All keys must be included in `required`.
+- All optional keys will have `null` added to their type.
+
+Reference: https://platform.openai.com/docs/guides/structured-outputs/supported-schemas
+"""
+function set_properties_strict!(parameters::AbstractDict)
+    parameters["additionalProperties"] = false
+    required_fields = get(parameters, "required", String[])
+    optional_fields = String[]
+
+    for (key, value) in parameters["properties"]
+        if key ∉ required_fields
+            push!(optional_fields, key)
+            if haskey(value, "type")
+                value["type"] = [value["type"], "null"]
+            end
+        end
+
+        # Recursively apply to nested properties
+        if haskey(value, "properties")
+            set_properties_strict!(value)
+        elseif haskey(value, "items") && haskey(value["items"], "properties")
+            ## if it's an array, we need to skip inside "items"
+            set_properties_strict!(value["items"])
+        end
+    end
+
+    parameters["required"] = vcat(required_fields, optional_fields)
+    return parameters
+end
+
 ######################
 # 2) Anthropic / XML format
 ######################
diff --git a/src/llm_openai.jl b/src/llm_openai.jl
index 4bee1ced2..fe866f022 100644
--- a/src/llm_openai.jl
+++ b/src/llm_openai.jl
@@ -969,6 +969,7 @@ end
             retries = 5,
             readtimeout = 120), api_kwargs::NamedTuple = (;
             tool_choice = "exact"),
+        strict::Union{Nothing, Bool} = nothing,
         kwargs...)
 
 Extract required information (defined by a struct **`return_type`**) from the provided prompt by leveraging OpenAI function calling mode.
@@ -994,6 +995,7 @@ It's effectively a light wrapper around `aigenerate` call, which requires additi
   - `tool_choice`: A string representing the tool choice to use for the API call. Usually, one of "auto","any","exact". 
     Defaults to `"exact"`, which is a made-up value to enforce the OpenAI requirements if we want one exact function.
     Providers like Mistral, Together, etc. use `"any"` instead.
+- `strict::Union{Nothing, Bool} = nothing`: A boolean indicating whether to enforce strict generation of the response (supported only for OpenAI models). It has additional latency for the first request. If `nothing`, standard function calling is used.
 - `kwargs`: Prompt variables to be used to fill the prompt/template
 
 # Returns
@@ -1100,11 +1102,13 @@ function aiextract(prompt_schema::AbstractOpenAISchema, prompt::ALLOWED_PROMPT_T
             retries = 5,
             readtimeout = 120), api_kwargs::NamedTuple = (;
             tool_choice = "exact"),
+        strict::Union{Nothing, Bool} = nothing,
         kwargs...)
     ##
     global MODEL_ALIASES
     ## Function calling specifics
-    tools = [Dict(:type => "function", :function => function_call_signature(return_type))]
+    tools = [Dict(
+        :type => "function", :function => function_call_signature(return_type; strict))]
     ## force our function to be used
     tool_choice_ = get(api_kwargs, :tool_choice, "exact")
     tool_choice = if tool_choice_ == "exact"
diff --git a/test/extraction.jl b/test/extraction.jl
index 476487321..e24cb9fa1 100644
--- a/test/extraction.jl
+++ b/test/extraction.jl
@@ -1,6 +1,6 @@
 using PromptingTools: MaybeExtract, extract_docstring, ItemsExtract
 using PromptingTools: has_null_type, is_required_field, remove_null_types, to_json_schema
-using PromptingTools: function_call_signature
+using PromptingTools: function_call_signature, set_properties_strict!
 
 # TODO: check more edge cases like empty structs
 
@@ -216,6 +216,100 @@ end
     @test schema_measurement["description"] ==
           "Represents person's age, height, and weight\n"
 end
+@testset "set_properties_strict!" begin
+    # Test 1: Basic functionality
+    params = Dict(
+        "properties" => Dict{String, Any}(
+            "name" => Dict{String, Any}("type" => "string"),
+            "age" => Dict{String, Any}("type" => "integer")
+        ),
+        "required" => ["name"]
+    )
+    set_properties_strict!(params)
+    @test params["additionalProperties"] == false
+    @test Set(params["required"]) == Set(["name", "age"])
+    @test params["properties"]["age"]["type"] == ["integer", "null"]
+
+    # Test 2: Nested properties
+    params = Dict{String, Any}(
+        "properties" => Dict{String, Any}(
+        "person" => Dict{String, Any}(
+        "type" => "object",
+        "properties" => Dict{String, Any}(
+            "name" => Dict{String, Any}("type" => "string"),
+            "age" => Dict{String, Any}("type" => "integer")
+        )
+    )
+    )
+    )
+    set_properties_strict!(params)
+    @test params["properties"]["person"]["additionalProperties"] == false
+    @test Set(params["properties"]["person"]["required"]) ==
+          Set(["name", "age"])
+
+    # Test 3: Array of objects
+    params = Dict{String, Any}(
+        "properties" => Dict{String, Any}(
+        "people" => Dict{String, Any}(
+        "type" => "array",
+        "items" => Dict{String, Any}(
+            "type" => "object",
+            "properties" => Dict{String, Any}(
+                "name" => Dict{String, Any}("type" => "string"),
+                "age" => Dict{String, Any}("type" => "integer")
+            )
+        )
+    )
+    )
+    )
+    set_properties_strict!(params)
+    @test params["properties"]["people"]["items"]["additionalProperties"] == false
+    @test Set(params["properties"]["people"]["items"]["required"]) == Set(["name", "age"])
+
+    # Test 4: Multiple levels of nesting
+    params = Dict{String, Any}(
+        "properties" => Dict{String, Any}(
+        "company" => Dict{String, Any}(
+        "type" => "object",
+        "properties" => Dict{String, Any}(
+            "name" => Dict{String, Any}("type" => "string"),
+            "employees" => Dict{String, Any}(
+                "type" => "array",
+                "items" => Dict{String, Any}(
+                    "type" => "object",
+                    "properties" => Dict{String, Any}(
+                        "name" => Dict{String, Any}("type" => "string"),
+                        "position" => Dict{String, Any}("type" => "string")
+                    )
+                )
+            )
+        )
+    )
+    )
+    )
+    set_properties_strict!(params)
+    @test params["properties"]["company"]["additionalProperties"] == false
+    @test params["properties"]["company"]["properties"]["employees"]["items"]["additionalProperties"] ==
+          false
+    @test Set(params["properties"]["company"]["properties"]["employees"]["items"]["required"]) ==
+          Set(["name", "position"])
+
+    # Test 5: Handling of existing required fields
+    params = Dict{String, Any}(
+        "properties" => Dict{String, Any}(
+            "name" => Dict{String, Any}("type" => "string"),
+            "age" => Dict{String, Any}("type" => "integer"),
+            "email" => Dict{String, Any}("type" => "string")
+        ),
+        "required" => ["name", "email"]
+    )
+    set_properties_strict!(params)
+    @test Set(params["required"]) == Set(["name", "email", "age"])
+    @test params["properties"]["age"]["type"] == ["integer", "null"]
+    @test !haskey(params["properties"]["name"], "null")
+    @test !haskey(params["properties"]["email"], "null")
+end
+
 @testset "function_call_signature" begin
     "Some docstring"
     struct MyMeasurement2
@@ -241,4 +335,49 @@ end
     ## MaybeWraper name cleanup
     schema = function_call_signature(MaybeExtract{MyMeasurement2})
     @test schema["name"] == "MaybeExtractMyMeasurement2_extractor"
-end
+
+    ## Test with strict = true
+
+    "Person's age, height, and weight."
+    struct MyMeasurement3
+        age::Int
+        height::Union{Int, Nothing}
+        weight::Union{Nothing, Float64}
+    end
+
+    # Test with strict = nothing (default behavior)
+    output_default = function_call_signature(MyMeasurement3)
+    @test !haskey(output_default, "strict")
+    @test output_default["name"] == "MyMeasurement3_extractor"
+    @test output_default["parameters"]["type"] == "object"
+    @test output_default["parameters"]["required"] == ["age"]
+    @test !haskey(output_default["parameters"], "additionalProperties")
+
+    # Test with strict =false
+    output_not_strict = function_call_signature(MyMeasurement3; strict = false)
+    @test haskey(output_not_strict, "strict")
+    @test output_not_strict["strict"] == false
+    @test output_not_strict["name"] == "MyMeasurement3_extractor"
+    @test output_not_strict["parameters"]["type"] == "object"
+    @test output_not_strict["parameters"]["required"] == ["age"]
+    @test !haskey(output_default["parameters"], "additionalProperties")
+
+    # Test with strict = true
+    output_strict = function_call_signature(MyMeasurement3; strict = true)
+    @test output_strict["strict"] == true
+    @test output_strict["name"] == "MyMeasurement3_extractor"
+    @test output_strict["parameters"]["type"] == "object"
+    @test Set(output_strict["parameters"]["required"]) == Set(["age", "height", "weight"])
+    @test output_strict["parameters"]["additionalProperties"] == false
+    @test output_strict["parameters"]["properties"]["height"]["type"] == ["integer", "null"]
+    @test output_strict["parameters"]["properties"]["weight"]["type"] == ["number", "null"]
+    @test output_strict["parameters"]["properties"]["age"]["type"] == "integer"
+
+    # Test with MaybeExtract wrapper
+    output_maybe = function_call_signature(MaybeExtract{MyMeasurement3}; strict = true)
+    @test output_maybe["name"] == "MaybeExtractMyMeasurement3_extractor"
+    @test output_maybe["parameters"]["properties"]["result"]["type"] == ["object", "null"]
+    @test output_maybe["parameters"]["properties"]["error"]["type"] == "boolean"
+    @test output_maybe["parameters"]["properties"]["message"]["type"] == ["string", "null"]
+    @test Set(output_maybe["parameters"]["required"]) == Set(["result", "error", "message"])
+end
\ No newline at end of file