diff --git a/anthropic.go b/anthropic.go
index 90ebdf5..aa81a90 100644
--- a/anthropic.go
+++ b/anthropic.go
@@ -134,15 +134,16 @@ func (a anthropic) requestToAnthropicRequest(req Request) anth.MessagesRequest {
 		}
 	}
 
-	if req.Toolbox != nil {
-		for _, tool := range req.Toolbox.funcs {
+	/*
+		for _, tool := range req.Toolbox.functions {
 			res.Tools = append(res.Tools, anth.ToolDefinition{
 				Name:        tool.Name,
 				Description: tool.Description,
-				InputSchema: tool.Parameters,
+				InputSchema: tool.Parameters.OpenAIParameters(),
 			})
 		}
-	}
+
+	*/
 
 	res.Messages = msgs
 
diff --git a/context.go b/context.go
index 8320269..0f8a838 100644
--- a/context.go
+++ b/context.go
@@ -7,9 +7,10 @@ import (
 
 type Context struct {
 	context.Context
-	request  Request
-	response *ResponseChoice
-	toolcall *ToolCall
+	request         Request
+	response        *ResponseChoice
+	toolcall        *ToolCall
+	syntheticFields map[string]string
 }
 
 func (c *Context) ToNewRequest(toolResults ...ToolCallResponse) Request {
@@ -55,20 +56,32 @@ func (c *Context) ToolCall() *ToolCall {
 	return c.toolcall
 }
 
+func (c *Context) SyntheticFields() map[string]string {
+	if c.syntheticFields == nil {
+		c.syntheticFields = map[string]string{}
+	}
+
+	return c.syntheticFields
+}
+
 func (c *Context) WithContext(ctx context.Context) *Context {
-	return &Context{Context: ctx, request: c.request, response: c.response, toolcall: c.toolcall}
+	return &Context{Context: ctx, request: c.request, response: c.response, toolcall: c.toolcall, syntheticFields: c.syntheticFields}
 }
 
 func (c *Context) WithRequest(request Request) *Context {
-	return &Context{Context: c.Context, request: request, response: c.response, toolcall: c.toolcall}
+	return &Context{Context: c.Context, request: request, response: c.response, toolcall: c.toolcall, syntheticFields: c.syntheticFields}
 }
 
 func (c *Context) WithResponse(response *ResponseChoice) *Context {
-	return &Context{Context: c.Context, request: c.request, response: response, toolcall: c.toolcall}
+	return &Context{Context: c.Context, request: c.request, response: response, toolcall: c.toolcall, syntheticFields: c.syntheticFields}
 }
 
 func (c *Context) WithToolCall(toolcall *ToolCall) *Context {
-	return &Context{Context: c.Context, request: c.request, response: c.response, toolcall: toolcall}
+	return &Context{Context: c.Context, request: c.request, response: c.response, toolcall: toolcall, syntheticFields: c.syntheticFields}
+}
+
+func (c *Context) WithSyntheticFields(syntheticFields map[string]string) *Context {
+	return &Context{Context: c.Context, request: c.request, response: c.response, toolcall: c.toolcall, syntheticFields: syntheticFields}
 }
 
 func (c *Context) Deadline() (deadline time.Time, ok bool) {
@@ -84,8 +97,19 @@ func (c *Context) Err() error {
 }
 
 func (c *Context) Value(key any) any {
-	if key == "request" {
+	switch key {
+	case "request":
 		return c.request
+
+	case "response":
+		return c.response
+
+	case "toolcall":
+		return c.toolcall
+
+	case "syntheticFields":
+		return c.syntheticFields
+
 	}
 	return c.Context.Value(key)
 }
diff --git a/function.go b/function.go
index 7ffe6b1..9bdd17a 100644
--- a/function.go
+++ b/function.go
@@ -4,11 +4,10 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"reflect"
 	"time"
 
-	"github.com/sashabaranov/go-openai"
-
 	"gitea.stevedudenhoeffer.com/steve/go-llm/schema"
 )
 
@@ -29,16 +28,63 @@ type Function struct {
 	paramType reflect.Type
 }
 
-func (f *Function) Execute(ctx *Context, input string) (any, error) {
+func (f Function) WithSyntheticField(name string, description string) Function {
+	if obj, o := f.Parameters.(schema.Object); o {
+		f.Parameters = obj.WithSyntheticField(name, description)
+	}
+
+	return f
+}
+
+func (f Function) WithSyntheticFields(fieldsAndDescriptions map[string]string) Function {
+	if obj, o := f.Parameters.(schema.Object); o {
+		for k, v := range fieldsAndDescriptions {
+			obj = obj.WithSyntheticField(k, v)
+		}
+		f.Parameters = obj
+	}
+
+	return f
+}
+
+func (f Function) Execute(ctx *Context, input string) (any, error) {
 	if !f.fn.IsValid() {
 		return "", fmt.Errorf("function %s is not implemented", f.Name)
 	}
 
+	slog.Info("Function.Execute", "name", f.Name, "input", input, "f", f.paramType)
 	// first, we need to parse the input into the struct
 	p := reflect.New(f.paramType)
 	fmt.Println("Function.Execute", f.Name, "input:", input)
-	//m := map[string]any{}
-	err := json.Unmarshal([]byte(input), p.Interface())
+
+	var vals map[string]any
+	err := json.Unmarshal([]byte(input), &vals)
+
+	var syntheticFields map[string]string
+
+	// first eat up any synthetic fields
+	if obj, o := f.Parameters.(schema.Object); o {
+		for k := range obj.SyntheticFields() {
+			key := schema.SyntheticFieldPrefix + k
+			if val, ok := vals[key]; ok {
+				if syntheticFields == nil {
+					syntheticFields = map[string]string{}
+				}
+
+				syntheticFields[k] = fmt.Sprint(val)
+				delete(vals, key)
+			}
+		}
+	}
+
+	// now for any remaining fields, re-marshal them into json and then unmarshal into the struct
+	b, err := json.Marshal(vals)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal input: %w (input: %s)", err, input)
+	}
+
+	// now we can unmarshal the input into the struct
+	err = json.Unmarshal(b, p.Interface())
 	if err != nil {
 		return "", fmt.Errorf("failed to unmarshal input: %w (input: %s)", err, input)
 	}
@@ -67,15 +113,6 @@ func (f *Function) Execute(ctx *Context, input string) (any, error) {
 	return exec(ctx)
 }
 
-func (f *Function) toOpenAIFunction() *openai.FunctionDefinition {
-	return &openai.FunctionDefinition{
-		Name:        f.Name,
-		Description: f.Description,
-		Strict:      f.Strict,
-		Parameters:  f.Parameters,
-	}
-}
-
 type FunctionCall struct {
 	Name      string `json:"name,omitempty"`
 	Arguments string `json:"arguments,omitempty"`
diff --git a/functions.go b/functions.go
index e1b7ccc..71a0a1c 100644
--- a/functions.go
+++ b/functions.go
@@ -13,7 +13,7 @@ import (
 // The struct parameters can have the following tags:
 // - Description: a string that describes the parameter, passed to openaiImpl to tell it what the parameter is for
 
-func NewFunction[T any](name string, description string, fn func(*Context, T) (any, error)) *Function {
+func NewFunction[T any](name string, description string, fn func(*Context, T) (any, error)) Function {
 	var o T
 
 	res := Function{
@@ -31,5 +31,5 @@ func NewFunction[T any](name string, description string, fn func(*Context, T) (a
 		panic("function parameter must be a struct")
 	}
 
-	return &res
+	return res
 }
diff --git a/go.mod b/go.mod
index 8454d65..e9596d7 100644
--- a/go.mod
+++ b/go.mod
@@ -5,8 +5,7 @@ go 1.23.1
 require (
 	github.com/google/generative-ai-go v0.19.0
 	github.com/liushuangls/go-anthropic/v2 v2.15.0
-	github.com/openai/openai-go v0.1.0-beta.6
-	github.com/sashabaranov/go-openai v1.38.1
+	github.com/openai/openai-go v0.1.0-beta.9
 	google.golang.org/api v0.228.0
 )
 
@@ -35,14 +34,14 @@ require (
 	go.opentelemetry.io/otel/metric v1.35.0 // indirect
 	go.opentelemetry.io/otel/trace v1.35.0 // indirect
 	golang.org/x/crypto v0.37.0 // indirect
-	golang.org/x/net v0.38.0 // indirect
+	golang.org/x/net v0.39.0 // indirect
 	golang.org/x/oauth2 v0.29.0 // indirect
 	golang.org/x/sync v0.13.0 // indirect
 	golang.org/x/sys v0.32.0 // indirect
 	golang.org/x/text v0.24.0 // indirect
 	golang.org/x/time v0.11.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20250404141209-ee84b53bf3d0 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20250404141209-ee84b53bf3d0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20250409194420-de1ac958c67a // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250409194420-de1ac958c67a // indirect
 	google.golang.org/grpc v1.71.1 // indirect
 	google.golang.org/protobuf v1.36.6 // indirect
 )
diff --git a/go.sum b/go.sum
index 869d1a3..331f8b6 100644
--- a/go.sum
+++ b/go.sum
@@ -37,10 +37,10 @@ github.com/liushuangls/go-anthropic/v2 v2.15.0 h1:zpplg7BRV/9FlMmeMPI0eDwhViB0l9
 github.com/liushuangls/go-anthropic/v2 v2.15.0/go.mod h1:kq2yW3JVy1/rph8u5KzX7F3q95CEpCT2RXp/2nfCmb4=
 github.com/openai/openai-go v0.1.0-beta.6 h1:JquYDpprfrGnlKvQQg+apy9dQ8R9mIrm+wNvAPp6jCQ=
 github.com/openai/openai-go v0.1.0-beta.6/go.mod h1:g461MYGXEXBVdV5SaR/5tNzNbSfwTBBefwc+LlDCK0Y=
+github.com/openai/openai-go v0.1.0-beta.9 h1:ABpubc5yU/3ejee2GgRrbFta81SG/d7bQbB8mIdP0Xo=
+github.com/openai/openai-go v0.1.0-beta.9/go.mod h1:g461MYGXEXBVdV5SaR/5tNzNbSfwTBBefwc+LlDCK0Y=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/sashabaranov/go-openai v1.38.1 h1:TtZabbFQZa1nEni/IhVtDF/WQjVqDgd+cWR5OeddzF8=
-github.com/sashabaranov/go-openai v1.38.1/go.mod h1:lj5b/K+zjTSFxVLijLSTDZuP7adOgerWeFyZLUhAKRg=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/tidwall/gjson v1.14.2/go.mod h1:/wbyibRr2FHMks5tjHJ5F8dMZh3AcwJEMf5vlfC0lxk=
@@ -73,6 +73,8 @@ golang.org/x/crypto v0.37.0 h1:kJNSjF/Xp7kU0iB2Z+9viTPMW4EqqsrywMXLJOOsXSE=
 golang.org/x/crypto v0.37.0/go.mod h1:vg+k43peMZ0pUMhYmVAWysMK35e6ioLh3wB8ZCAfbVc=
 golang.org/x/net v0.38.0 h1:vRMAPTMaeGqVhG5QyLJHqNDwecKTomGeqbnfZyKlBI8=
 golang.org/x/net v0.38.0/go.mod h1:ivrbrMbzFq5J41QOQh0siUuly180yBYtLp+CKbEaFx8=
+golang.org/x/net v0.39.0 h1:ZCu7HMWDxpXpaiKdhzIfaltL9Lp31x/3fCP11bc6/fY=
+golang.org/x/net v0.39.0/go.mod h1:X7NRbYVEA+ewNkCNyJ513WmMdQ3BineSwVtN2zD/d+E=
 golang.org/x/oauth2 v0.29.0 h1:WdYw2tdTK1S8olAzWHdgeqfy+Mtm9XNhv/xJsY65d98=
 golang.org/x/oauth2 v0.29.0/go.mod h1:onh5ek6nERTohokkhCD/y2cV4Do3fxFHFuAejCkRWT8=
 golang.org/x/sync v0.13.0 h1:AauUjRAJ9OSnvULf/ARrrVywoJDy0YS2AwQ98I37610=
@@ -87,8 +89,12 @@ google.golang.org/api v0.228.0 h1:X2DJ/uoWGnY5obVjewbp8icSL5U4FzuCfy9OjbLSnLs=
 google.golang.org/api v0.228.0/go.mod h1:wNvRS1Pbe8r4+IfBIniV8fwCpGwTrYa+kMUDiC5z5a4=
 google.golang.org/genproto/googleapis/api v0.0.0-20250404141209-ee84b53bf3d0 h1:Qbb5RVn5xzI4naMJSpJ7lhvmos6UwZkbekd5Uz7rt9E=
 google.golang.org/genproto/googleapis/api v0.0.0-20250404141209-ee84b53bf3d0/go.mod h1:6T35kB3IPpdw7Wul09by0G/JuOuIFkXV6OOvt8IZeT8=
+google.golang.org/genproto/googleapis/api v0.0.0-20250409194420-de1ac958c67a h1:OQ7sHVzkx6L57dQpzUS4ckfWJ51KDH74XHTDe23xWAs=
+google.golang.org/genproto/googleapis/api v0.0.0-20250409194420-de1ac958c67a/go.mod h1:2R6XrVC8Oc08GlNh8ujEpc7HkLiEZ16QeY7FxIs20ac=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20250404141209-ee84b53bf3d0 h1:0K7wTWyzxZ7J+L47+LbFogJW1nn/gnnMCN0vGXNYtTI=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20250404141209-ee84b53bf3d0/go.mod h1:qQ0YXyHHx3XkvlzUtpXDkS29lDSafHMZBAZDc03LQ3A=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250409194420-de1ac958c67a h1:GIqLhp/cYUkuGuiT+vJk8vhOP86L4+SP5j8yXgeVpvI=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250409194420-de1ac958c67a/go.mod h1:qQ0YXyHHx3XkvlzUtpXDkS29lDSafHMZBAZDc03LQ3A=
 google.golang.org/grpc v1.71.1 h1:ffsFWr7ygTUscGPI0KKK6TLrGz0476KUvvsbqWK0rPI=
 google.golang.org/grpc v1.71.1/go.mod h1:H0GRtasmQOh9LkFoCPDu3ZrwUtD1YGE+b2vYBYd/8Ec=
 google.golang.org/protobuf v1.36.6 h1:z1NpPI8ku2WgiWnf+t9wTPsn6eP1L7ksHUlkfLvd9xY=
diff --git a/google.go b/google.go
index 8eea66f..b371978 100644
--- a/google.go
+++ b/google.go
@@ -23,25 +23,22 @@ func (g google) ModelVersion(modelVersion string) (ChatCompletion, error) {
 func (g google) requestToChatHistory(in Request, model *genai.GenerativeModel) (*genai.GenerativeModel, *genai.ChatSession, []genai.Part) {
 	res := *model
 
-	if in.Toolbox != nil {
-		for _, tool := range in.Toolbox.funcs {
-
-			res.Tools = append(res.Tools, &genai.Tool{
-				FunctionDeclarations: []*genai.FunctionDeclaration{
-					{
-						Name:        tool.Name,
-						Description: tool.Description,
-						Parameters:  tool.Parameters.GoogleParameters(),
-					},
+	for _, tool := range in.Toolbox.functions {
+		res.Tools = append(res.Tools, &genai.Tool{
+			FunctionDeclarations: []*genai.FunctionDeclaration{
+				{
+					Name:        tool.Name,
+					Description: tool.Description,
+					Parameters:  tool.Parameters.GoogleParameters(),
 				},
-			})
-		}
+			},
+		})
+	}
 
-		if !in.Toolbox.dontRequireTool {
-			res.ToolConfig = &genai.ToolConfig{FunctionCallingConfig: &genai.FunctionCallingConfig{
-				Mode: genai.FunctionCallingAny,
-			}}
-		}
+	if !in.Toolbox.RequiresTool() {
+		res.ToolConfig = &genai.ToolConfig{FunctionCallingConfig: &genai.FunctionCallingConfig{
+			Mode: genai.FunctionCallingAny,
+		}}
 	}
 
 	cs := res.StartChat()
diff --git a/openai.go b/openai.go
index 80c6d40..929ab6c 100644
--- a/openai.go
+++ b/openai.go
@@ -31,23 +31,21 @@ func (o openaiImpl) newRequestToOpenAIRequest(request Request) openai.ChatComple
 		res.Messages = append(res.Messages, msg.toChatCompletionMessages(o.model)...)
 	}
 
-	if request.Toolbox != nil {
-		for _, tool := range request.Toolbox.funcs {
-			res.Tools = append(res.Tools, openai.ChatCompletionToolParam{
-				Type: "function",
-				Function: shared.FunctionDefinitionParam{
-					Name:        tool.Name,
-					Description: openai.String(tool.Description),
-					Strict:      openai.Bool(tool.Strict),
-					Parameters:  tool.Parameters.OpenAIParameters(),
-				},
-			})
-		}
+	for _, tool := range request.Toolbox.functions {
+		res.Tools = append(res.Tools, openai.ChatCompletionToolParam{
+			Type: "function",
+			Function: shared.FunctionDefinitionParam{
+				Name:        tool.Name,
+				Description: openai.String(tool.Description),
+				Strict:      openai.Bool(tool.Strict),
+				Parameters:  tool.Parameters.OpenAIParameters(),
+			},
+		})
+	}
 
-		if !request.Toolbox.dontRequireTool {
-			res.ToolChoice = openai.ChatCompletionToolChoiceOptionUnionParam{
-				OfAuto: openai.String("required"),
-			}
+	if request.Toolbox.RequiresTool() {
+		res.ToolChoice = openai.ChatCompletionToolChoiceOptionUnionParam{
+			OfAuto: openai.String("required"),
 		}
 	}
 
diff --git a/request.go b/request.go
index 961fae7..1a39e33 100644
--- a/request.go
+++ b/request.go
@@ -15,7 +15,7 @@ type Input interface {
 type Request struct {
 	Conversation []Input
 	Messages     []Message
-	Toolbox      *ToolBox
+	Toolbox      ToolBox
 	Temperature  *float64
 }
 
diff --git a/schema/GetType.go b/schema/GetType.go
index 4aa365b..342dea2 100644
--- a/schema/GetType.go
+++ b/schema/GetType.go
@@ -25,27 +25,27 @@ func getFromType(t reflect.Type, b basic) Type {
 
 	switch t.Kind() {
 	case reflect.String:
-		b.DataType = String
+		b.DataType = TypeString
 		b.typeName = "string"
 		return b
 
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		b.DataType = Integer
+		b.DataType = TypeInteger
 		b.typeName = "integer"
 		return b
 
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
-		b.DataType = Integer
+		b.DataType = TypeInteger
 		b.typeName = "integer"
 		return b
 
 	case reflect.Float32, reflect.Float64:
-		b.DataType = Number
+		b.DataType = TypeNumber
 		b.typeName = "number"
 		return b
 
 	case reflect.Bool:
-		b.DataType = Boolean
+		b.DataType = TypeBoolean
 		b.typeName = "boolean"
 		return b
 
@@ -92,7 +92,7 @@ func getField(f reflect.StructField, index int) Type {
 			}
 		}
 
-		b.DataType = String
+		b.DataType = TypeString
 		b.typeName = "string"
 		return enum{
 			basic:  b,
@@ -104,15 +104,26 @@ func getField(f reflect.StructField, index int) Type {
 	return getFromType(t, b)
 }
 
-func getObject(t reflect.Type) object {
+func getObject(t reflect.Type) Object {
 	fields := make(map[string]Type, t.NumField())
 	for i := 0; i < t.NumField(); i++ {
 		field := t.Field(i)
-		fields[field.Name] = getField(field, i)
+
+		if field.Anonymous {
+			// if the field is anonymous, we need to get the fields of the anonymous struct
+			// and add them to the object
+			anon := getObject(field.Type)
+			for k, v := range anon.fields {
+				fields[k] = v
+			}
+			continue
+		} else {
+			fields[field.Name] = getField(field, i)
+		}
 	}
 
-	return object{
-		basic:  basic{DataType: Object, typeName: "object"},
+	return Object{
+		basic:  basic{DataType: TypeObject, typeName: "object"},
 		fields: fields,
 	}
 }
@@ -120,7 +131,7 @@ func getObject(t reflect.Type) object {
 func getArray(t reflect.Type) array {
 	res := array{
 		basic: basic{
-			DataType: Array,
+			DataType: TypeArray,
 			typeName: "array",
 		},
 	}
diff --git a/schema/basic.go b/schema/basic.go
index e7f824c..087b794 100644
--- a/schema/basic.go
+++ b/schema/basic.go
@@ -15,12 +15,12 @@ var _ Type = basic{}
 type DataType string
 
 const (
-	String  DataType = "string"
-	Integer DataType = "integer"
-	Number  DataType = "number"
-	Boolean DataType = "boolean"
-	Object  DataType = "object"
-	Array   DataType = "array"
+	TypeString  DataType = "string"
+	TypeInteger DataType = "integer"
+	TypeNumber  DataType = "number"
+	TypeBoolean DataType = "boolean"
+	TypeObject  DataType = "object"
+	TypeArray   DataType = "array"
 )
 
 type basic struct {
@@ -49,17 +49,17 @@ func (b basic) GoogleParameters() *genai.Schema {
 	var t = genai.TypeUnspecified
 
 	switch b.DataType {
-	case String:
+	case TypeString:
 		t = genai.TypeString
-	case Integer:
+	case TypeInteger:
 		t = genai.TypeInteger
-	case Number:
+	case TypeNumber:
 		t = genai.TypeNumber
-	case Boolean:
+	case TypeBoolean:
 		t = genai.TypeBoolean
-	case Object:
+	case TypeObject:
 		t = genai.TypeObject
-	case Array:
+	case TypeArray:
 		t = genai.TypeArray
 	default:
 		t = genai.TypeUnspecified
@@ -82,12 +82,12 @@ func (b basic) FromAny(val any) (reflect.Value, error) {
 	v := reflect.ValueOf(val)
 
 	switch b.DataType {
-	case String:
+	case TypeString:
 		var val = v.String()
 
 		return reflect.ValueOf(val), nil
 
-	case Integer:
+	case TypeInteger:
 		if v.Kind() == reflect.Float64 {
 			return v.Convert(reflect.TypeOf(int(0))), nil
 		} else if v.Kind() != reflect.Int {
@@ -96,7 +96,7 @@ func (b basic) FromAny(val any) (reflect.Value, error) {
 			return v, nil
 		}
 
-	case Number:
+	case TypeNumber:
 		if v.Kind() == reflect.Float64 {
 			return v.Convert(reflect.TypeOf(float64(0))), nil
 		} else if v.Kind() != reflect.Float64 {
@@ -105,7 +105,7 @@ func (b basic) FromAny(val any) (reflect.Value, error) {
 			return v, nil
 		}
 
-	case Boolean:
+	case TypeBoolean:
 		if v.Kind() == reflect.Bool {
 			return v, nil
 		} else if v.Kind() == reflect.String {
diff --git a/schema/object.go b/schema/object.go
index 3dd733d..7e96c44 100644
--- a/schema/object.go
+++ b/schema/object.go
@@ -8,15 +8,44 @@ import (
 	"github.com/openai/openai-go"
 )
 
-type object struct {
+const (
+	// SyntheticFieldPrefix is any prefix that is added to any synthetic fields that are added to the object, to prevent
+	// collisions with the fields in the struct.
+	SyntheticFieldPrefix = "__"
+)
+
+type Object struct {
 	basic
 
 	ref reflect.Type
 
 	fields map[string]Type
+
+	// syntheticFields are fields that are not in the struct but are generated by a system.
+	synetheticFields map[string]Type
 }
 
-func (o object) OpenAIParameters() openai.FunctionParameters {
+func (o Object) WithSyntheticField(name string, description string) Object {
+	if o.synetheticFields == nil {
+		o.synetheticFields = map[string]Type{}
+	}
+
+	o.synetheticFields[name] = basic{
+		DataType:    TypeString,
+		typeName:    "string",
+		index:       -1,
+		required:    false,
+		description: description,
+	}
+
+	return o
+}
+
+func (o Object) SyntheticFields() map[string]Type {
+	return o.synetheticFields
+}
+
+func (o Object) OpenAIParameters() openai.FunctionParameters {
 	var properties = map[string]openai.FunctionParameters{}
 	var required []string
 	for k, v := range o.fields {
@@ -26,6 +55,13 @@ func (o object) OpenAIParameters() openai.FunctionParameters {
 		}
 	}
 
+	for k, v := range o.synetheticFields {
+		properties[SyntheticFieldPrefix+k] = v.OpenAIParameters()
+		if v.Required() {
+			required = append(required, SyntheticFieldPrefix+k)
+		}
+	}
+
 	var res = openai.FunctionParameters{
 		"type":        "object",
 		"description": o.Description(),
@@ -39,7 +75,7 @@ func (o object) OpenAIParameters() openai.FunctionParameters {
 	return res
 }
 
-func (o object) GoogleParameters() *genai.Schema {
+func (o Object) GoogleParameters() *genai.Schema {
 	var properties = map[string]*genai.Schema{}
 	var required []string
 	for k, v := range o.fields {
@@ -62,7 +98,8 @@ func (o object) GoogleParameters() *genai.Schema {
 	return res
 }
 
-func (o object) FromAny(val any) (reflect.Value, error) {
+// FromAny converts the value from any to the correct type, returning the value, and an error if any
+func (o Object) FromAny(val any) (reflect.Value, error) {
 	// if the value is nil, we can't do anything
 	if val == nil {
 		return reflect.Value{}, nil
@@ -99,7 +136,7 @@ func (o object) FromAny(val any) (reflect.Value, error) {
 	return obj, nil
 }
 
-func (o object) SetValueOnField(obj reflect.Value, val reflect.Value) {
+func (o Object) SetValueOnField(obj reflect.Value, val reflect.Value) {
 	// if this basic type is not required that means it's a pointer type so we need to set the value to the address of the value
 	if !o.required {
 		val = val.Addr()
diff --git a/toolbox.go b/toolbox.go
index 61fb44e..6737362 100644
--- a/toolbox.go
+++ b/toolbox.go
@@ -4,79 +4,82 @@ import (
 	"context"
 	"errors"
 	"fmt"
-
-	"github.com/sashabaranov/go-openai"
 )
 
 // ToolBox is a collection of tools that OpenAI can use to execute functions.
 // It is a wrapper around a collection of functions, and provides a way to automatically call the correct function with
 // the correct parameters.
 type ToolBox struct {
-	funcs           []Function
-	names           map[string]Function
+	functions       map[string]Function
 	dontRequireTool bool
 }
 
-func NewToolBox(fns ...*Function) *ToolBox {
+func NewToolBox(fns ...Function) ToolBox {
 	res := ToolBox{
-		funcs: []Function{},
-		names: map[string]Function{},
+		functions: map[string]Function{},
 	}
 
 	for _, f := range fns {
-		o := *f
-		res.names[o.Name] = o
-		res.funcs = append(res.funcs, o)
-	}
-
-	return &res
-}
-
-func (t *ToolBox) WithFunction(f Function) *ToolBox {
-	t2 := *t
-	t2.names[f.Name] = f
-	t2.funcs = append(t2.funcs, f)
-
-	return &t2
-}
-
-func (t *ToolBox) WithFunctionRemoved(name string) *ToolBox {
-	t2 := *t
-
-	delete(t2.names, name)
-
-	for i, f := range t2.funcs {
-		if f.Name == name {
-			t2.funcs = append(t2.funcs[:i], t2.funcs[i+1:]...)
-			break
-		}
-	}
-
-	return &t2
-}
-
-func (t *ToolBox) WithRequireTool(val bool) *ToolBox {
-	t2 := *t
-	t2.dontRequireTool = !val
-	return &t2
-}
-
-// ToOpenAI will convert the current ToolBox to a slice of openai.Tool, which can be used to send to the OpenAI API.
-func (t *ToolBox) toOpenAI() []openai.Tool {
-	var res []openai.Tool
-
-	for _, f := range t.funcs {
-		res = append(res, openai.Tool{
-			Type:     "function",
-			Function: f.toOpenAIFunction(),
-		})
+		res.functions[f.Name] = f
 	}
 
 	return res
 }
 
-func (t *ToolBox) ToToolChoice() any {
-	if len(t.funcs) == 0 {
+func (t ToolBox) Functions() []Function {
+	var res []Function
+
+	for _, f := range t.functions {
+		res = append(res, f)
+	}
+
+	return res
+}
+
+func (t ToolBox) WithFunction(f Function) ToolBox {
+	t.functions[f.Name] = f
+
+	return t
+}
+
+func (t ToolBox) WithFunctions(fns ...Function) ToolBox {
+	for _, f := range fns {
+		t.functions[f.Name] = f
+	}
+
+	return t
+}
+
+func (t ToolBox) WithSyntheticFieldsAddedToAllFunctions(fieldsAndDescriptions map[string]string) ToolBox {
+	for k, v := range t.functions {
+		t.functions[k] = v.WithSyntheticFields(fieldsAndDescriptions)
+	}
+
+	return t
+}
+
+func (t ToolBox) ForEachFunction(fn func(f Function)) {
+	for _, f := range t.functions {
+		fn(f)
+	}
+}
+
+func (t ToolBox) WithFunctionRemoved(name string) ToolBox {
+	delete(t.functions, name)
+	return t
+}
+
+func (t ToolBox) WithRequireTool(val bool) ToolBox {
+	t.dontRequireTool = !val
+	return t
+}
+
+func (t ToolBox) RequiresTool() bool {
+	return !t.dontRequireTool && len(t.functions) > 0
+}
+
+func (t ToolBox) ToToolChoice() any {
+	if len(t.functions) == 0 {
 		return nil
 	}
 
@@ -87,8 +90,8 @@ var (
 	ErrFunctionNotFound = errors.New("function not found")
 )
 
-func (t *ToolBox) executeFunction(ctx *Context, functionName string, params string) (any, error) {
-	f, ok := t.names[functionName]
+func (t ToolBox) executeFunction(ctx *Context, functionName string, params string) (any, error) {
+	f, ok := t.functions[functionName]
 
 	if !ok {
 		return "", newError(ErrFunctionNotFound, fmt.Errorf("function \"%s\" not found", functionName))
@@ -97,14 +100,29 @@ func (t *ToolBox) executeFunction(ctx *Context, functionName string, params stri
 	return f.Execute(ctx, params)
 }
 
-func (t *ToolBox) Execute(ctx *Context, toolCall ToolCall) (any, error) {
+func (t ToolBox) Execute(ctx *Context, toolCall ToolCall) (any, error) {
 	return t.executeFunction(ctx.WithToolCall(&toolCall), toolCall.FunctionCall.Name, toolCall.FunctionCall.Arguments)
 }
 
+func (t ToolBox) GetSyntheticParametersFromFunctionContext(ctx context.Context) map[string]string {
+	val := ctx.Value("syntheticParameters")
+
+	if val == nil {
+		return nil
+	}
+
+	syntheticParameters, ok := val.(map[string]string)
+	if !ok {
+		return nil
+	}
+
+	return syntheticParameters
+}
+
 // ExecuteCallbacks will execute all the tool calls in the given list, and call the given callbacks when a new function is created, and when a function is finished.
 // OnNewFunction is called when a new function is created
 // OnFunctionFinished is called when a function is finished
-func (t *ToolBox) ExecuteCallbacks(ctx *Context, toolCalls []ToolCall, OnNewFunction func(ctx context.Context, funcName string, parameter string) (any, error), OnFunctionFinished func(ctx context.Context, funcName string, parameter string, result any, err error, newFunctionResult any) error) ([]ToolCallResponse, error) {
+func (t ToolBox) ExecuteCallbacks(ctx *Context, toolCalls []ToolCall, OnNewFunction func(ctx context.Context, funcName string, parameter string) (any, error), OnFunctionFinished func(ctx context.Context, funcName string, parameter string, result any, err error, newFunctionResult any) error) ([]ToolCallResponse, error) {
 	var res []ToolCallResponse
 
 	for _, call := range toolCalls {