diff --git a/CHANGELOG.md b/CHANGELOG.md
index 94519551b..1118085b1 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
 
+## [0.62.1]
+
+### Fixed
+- Fixed a bug in `tool_call_signature` where hidden fields were not hidden early enough and would fail if a Dict argument was provided. It used to do the processing after, but Dicts cannot be processed, so we're now masking the fields upfront.
+
 ## [0.62.0]
 
 ### Added
diff --git a/Project.toml b/Project.toml
index 096f7d153..c2d232ab7 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 = "0.62.0"
+version = "0.62.1"
 
 [deps]
 AbstractTrees = "1520ce14-60c1-5f80-bbc7-55ef81b5835c"
diff --git a/src/extraction.jl b/src/extraction.jl
index a3d144de1..780aaf121 100644
--- a/src/extraction.jl
+++ b/src/extraction.jl
@@ -181,7 +181,17 @@ function extract_docstring(m::Method; max_description_length::Int = 100)
     return extract_docstring(get_function(m); max_description_length)
 end
 
-function to_json_schema(orig_type; max_description_length::Int = 100)
+@inline function is_hidden_field(field_name::AbstractString,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}})
+    any(x -> occursin(x, field_name), hidden_fields)
+end
+@inline function is_hidden_field(field_name::Symbol,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}})
+    is_hidden_field(string(field_name), hidden_fields)
+end
+
+function to_json_schema(orig_type; max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[])
     schema = Dict{String, Any}()
     type = remove_null_types(orig_type)
     if isstructtype(type)
@@ -190,9 +200,12 @@ function to_json_schema(orig_type; max_description_length::Int = 100)
         ## extract the field names and types
         required_types = String[]
         for (field_name, field_type) in zip(fieldnames(type), fieldtypes(type))
+            if is_hidden_field(field_name, hidden_fields)
+                continue
+            end
             schema["properties"][string(field_name)] = to_json_schema(
                 remove_null_types(field_type);
-                max_description_length)
+                max_description_length, hidden_fields)
             ## Hack: no null type (Nothing, Missing) implies it it is a required field
             is_required_field(field_type) && push!(required_types, string(field_name))
         end
@@ -205,23 +218,29 @@ function to_json_schema(orig_type; max_description_length::Int = 100)
     end
     return schema
 end
-function to_json_schema(type::Type{<:AbstractString}; max_description_length::Int = 100)
+function to_json_schema(type::Type{<:AbstractString}; max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[])
     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}}
+        max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[]) where {T <:
+                                                                                         Union{
+        AbstractSet, Tuple, AbstractArray}}
     element_type = eltype(type)
     return Dict{String, Any}("type" => "array",
-        "items" => to_json_schema(remove_null_types(element_type)))
+        "items" => to_json_schema(remove_null_types(element_type);
+            max_description_length, hidden_fields))
 end
-function to_json_schema(type::Type{<:Enum}; max_description_length::Int = 100)
+function to_json_schema(type::Type{<:Enum}; max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[])
     enum_options = Base.Enums.namemap(type) |> values .|> string
     return Dict{String, Any}("type" => "string",
         "enum" => enum_options)
 end
 ## Dispatch for method of a function -- grabs only arguments!! Not kwargs!!
-function to_json_schema(m::Method; max_description_length::Int = 100)
+function to_json_schema(m::Method; max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[])
     ## Warning: We cannot extract keyword arguments from the method signature
     kwargs = Base.kwarg_decl(m)
     !isempty(kwargs) &&
@@ -233,9 +252,12 @@ function to_json_schema(m::Method; max_description_length::Int = 100)
     ## extract the field names and types
     required_types = String[]
     for (field_name, field_type) in zip(get_arg_names(m), get_arg_types(m))
+        if is_hidden_field(field_name, hidden_fields)
+            continue
+        end
         schema["properties"][string(field_name)] = to_json_schema(
             remove_null_types(field_type);
-            max_description_length)
+            max_description_length, hidden_fields)
         ## Hack: no null type (Nothing, Missing) implies it it is a required field
         is_required_field(field_type) && push!(required_types, string(field_name))
     end
@@ -245,7 +267,8 @@ function to_json_schema(m::Method; max_description_length::Int = 100)
     !isempty(docs) && (schema["description"] = docs)
     return schema
 end
-function to_json_schema(type::Type{<:AbstractDict}; max_description_length::Int = 100)
+function to_json_schema(type::Type{<:AbstractDict}; max_description_length::Int = 100,
+        hidden_fields::AbstractVector{<:Union{AbstractString, Regex}} = String[])
     throw(ArgumentError("Dicts are not supported yet as we cannot analyze their keys/values on a type-level. Use a nested Struct instead!"))
 end
 
@@ -535,7 +558,8 @@ function tool_call_signature(
         name
     end
     schema = Dict{String, Any}("name" => name,
-        "parameters" => to_json_schema(type_or_method; max_description_length))
+        "parameters" => to_json_schema(type_or_method; max_description_length,
+            hidden_fields))
     ## docstrings
     docs = isnothing(docs) ? extract_docstring(type_or_method; max_description_length) :
            docs
diff --git a/test/extraction.jl b/test/extraction.jl
index cffd8d441..3f8617558 100644
--- a/test/extraction.jl
+++ b/test/extraction.jl
@@ -6,7 +6,7 @@ using PromptingTools: Tool, isabstracttool, execute_tool, parse_tool, get_arg_na
                       get_arg_types, get_method, get_function, remove_field!,
                       tool_call_signature, ToolRef
 using PromptingTools: AbstractToolError, ToolNotFoundError, ToolExecutionError,
-                      ToolGenericError
+                      ToolGenericError, is_hidden_field
 
 # TODO: check more edge cases like empty structs
 
@@ -358,6 +358,36 @@ end
     @test schema_measurement["description"] ==
           "Represents person's age, height, and weight\n"
 end
+
+@testset "is_hidden_field" begin
+    # Test basic string matching
+    @test is_hidden_field("context", ["context"]) == true
+    @test is_hidden_field("data", ["context"]) == false
+
+    # Test regex matching
+    @test is_hidden_field("my_context", [r"context$"]) == true
+    @test is_hidden_field("context_var", [r"^context"]) == true
+    @test is_hidden_field("mydata", [r"context"]) == false
+
+    # Test multiple patterns
+    @test is_hidden_field("context", ["data", "context", "temp"]) == true
+    @test is_hidden_field("context", [r"^data", r"temp$", r"context"]) == true
+
+    # Test mixed string and regex patterns
+    @test is_hidden_field(
+        "my_context", Union{AbstractString, Regex}["data", r"context$"]) == true
+    @test is_hidden_field(
+        "context_var", Union{AbstractString, Regex}[r"^context", "temp"]) == true
+
+    # Test empty patterns list
+    @test is_hidden_field("context", String[]) == false
+    @test is_hidden_field("context", Regex[]) == false
+
+    # Test with Symbol input
+    @test is_hidden_field(:context, ["context"]) == true
+    @test is_hidden_field(:my_context, [r"context$"]) == true
+    @test is_hidden_field(:data, ["context"]) == false
+end
 @testset "set_properties_strict!" begin
     # Test 1: Basic functionality
     params = Dict(
@@ -769,6 +799,20 @@ end
     tool = ToolRef(; ref = :computer, callable = println)
     tool_map = tool_call_signature(tool)
     @test tool_map == Dict("computer" => tool)
+
+    ## accepting dictionary when it's hidden // it would fail otherwise
+    tool_map = tool_call_signature(context_test_function2; hidden_fields = ["context"])
+    @test tool_map isa Dict
+
+    @test_throws ArgumentError tool_call_signature(context_test_function2)
+
+    # for struct
+    mutable struct MyStruct1234
+        context::Dict{String, Any}
+    end
+    @test_throws ArgumentError tool_call_signature(MyStruct1234)
+    tool_map = tool_call_signature(MyStruct1234; hidden_fields = ["context"])
+    @test tool_map isa Dict
 end
 
 @testset "parse_tool" begin