diff --git a/inlay_hints.go b/inlay_hints.go
new file mode 100644
index 0000000..a294657
--- /dev/null
+++ b/inlay_hints.go
@@ -0,0 +1,207 @@
+package protocol
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+const (
+	// MethodTextDocumentInlayHint method name of `textDocument/inlayHint`.
+	MethodTextDocumentInlayHint = "textDocument/inlayHint"
+)
+
+// InlayHintParams - Parameters for a `textDocument/inlayHint` request.
+//
+// @since 3.17.0
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#inlayHintParams
+type InlayHintParams struct {
+	WorkDoneProgressParams
+	PartialResultParams
+
+	// The text document.
+	TextDocument TextDocumentIdentifier `json:"textDocument"`
+
+	// The visible range for which inlay hints should be computed.
+	Range Range `json:"range"`
+}
+
+// InlayHintKind - The kind of an inlay hint.
+//
+// @since 3.17.0
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#inlayHintKind
+type InlayHintKind int
+
+const (
+	// InlayHintKindType - An inlay hint that shows a type annotation.
+	InlayHintKindType InlayHintKind = 1
+
+	// InlayHintKindParameter - An inlay hint that shows a parameter name.
+	InlayHintKindParameter InlayHintKind = 2
+)
+
+// InlayHintTooltip can be a plain string or a MarkupContent object.
+//
+// @since 3.17.0
+type InlayHintTooltip struct {
+	String        *string
+	MarkupContent *MarkupContent
+}
+
+func (t InlayHintTooltip) MarshalJSON() ([]byte, error) {
+	if t.String != nil {
+		return json.Marshal(*t.String)
+	}
+	if t.MarkupContent != nil {
+		return json.Marshal(t.MarkupContent)
+	}
+	return []byte("null"), nil
+}
+
+func (t *InlayHintTooltip) UnmarshalJSON(data []byte) error {
+	*t = InlayHintTooltip{}
+
+	if string(data) == "null" {
+		return nil
+	}
+
+	var str string
+	if err := json.Unmarshal(data, &str); err == nil {
+		t.String = &str
+		return nil
+	}
+
+	var markup MarkupContent
+	if err := json.Unmarshal(data, &markup); err == nil && markup.Kind != "" {
+		t.MarkupContent = &markup
+		return nil
+	}
+
+	return errors.New("invalid InlayHintTooltip: not string, MarkupContent, or null")
+}
+
+// InlayHintLabelPart - A segment of an inlay hint label.
+//
+// @since 3.17.0
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#inlayHintLabelPart
+type InlayHintLabelPart struct {
+	// The mandatory label value.
+	Value string `json:"value"`
+
+	// The tooltip text or markup shown when hovering this label part.
+	Tooltip *InlayHintTooltip `json:"tooltip,omitempty"`
+
+	// A source location for this label part.
+	Location *Location `json:"location,omitempty"`
+
+	// A command associated with this label part.
+	Command *Command `json:"command,omitempty"`
+}
+
+// InlayHintLabel can be either a string or a list of label parts.
+//
+// @since 3.17.0
+type InlayHintLabel struct {
+	String *string
+	Parts  []InlayHintLabelPart
+}
+
+func (l InlayHintLabel) MarshalJSON() ([]byte, error) {
+	if l.String != nil {
+		return json.Marshal(*l.String)
+	}
+	if l.Parts != nil {
+		return json.Marshal(l.Parts)
+	}
+	return nil, errors.New("one of InlayHintLabel.String or InlayHintLabel.Parts needs to be set")
+}
+
+func (l *InlayHintLabel) UnmarshalJSON(data []byte) error {
+	*l = InlayHintLabel{}
+
+	var str string
+	if err := json.Unmarshal(data, &str); err == nil {
+		l.String = &str
+		return nil
+	}
+
+	var parts []InlayHintLabelPart
+	if err := json.Unmarshal(data, &parts); err == nil {
+		l.Parts = parts
+		return nil
+	}
+
+	return errors.New("invalid InlayHintLabel: not string or []InlayHintLabelPart")
+}
+
+// InlayHint represents an inlay hint item.
+//
+// @since 3.17.0
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#inlayHint
+type InlayHint struct {
+	// The position of this hint.
+	Position Position `json:"position"`
+
+	// The label of this hint. A human readable string or an array of label parts.
+	Label InlayHintLabel `json:"label"`
+
+	// The kind of this hint.
+	Kind *InlayHintKind `json:"kind,omitempty"`
+
+	// Optional text edits that are performed when accepting this hint.
+	TextEdits []TextEdit `json:"textEdits,omitempty"`
+
+	// The tooltip text when hovering over this hint.
+	Tooltip *InlayHintTooltip `json:"tooltip,omitempty"`
+
+	// Render padding before this hint.
+	PaddingLeft *bool `json:"paddingLeft,omitempty"`
+
+	// Render padding after this hint.
+	PaddingRight *bool `json:"paddingRight,omitempty"`
+
+	// A data entry field preserved between a hint request and resolve request.
+	Data LSPAny `json:"data,omitempty"`
+}
+
+// InlayHintResponse - Result for a `textDocument/inlayHint` request.
+//
+// It is either an array of `InlayHint` or `null`.
+//
+// @since 3.17.0
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#inlayHint
+type InlayHintResponse struct {
+	Hints []InlayHint
+	Null  bool
+}
+
+func (r InlayHintResponse) MarshalJSON() ([]byte, error) {
+	if r.Null {
+		return []byte("null"), nil
+	}
+	if r.Hints == nil {
+		return []byte("null"), nil
+	}
+	return json.Marshal(r.Hints)
+}
+
+func (r *InlayHintResponse) UnmarshalJSON(data []byte) error {
+	*r = InlayHintResponse{}
+
+	if string(data) == "null" {
+		r.Null = true
+		return nil
+	}
+
+	var hints []InlayHint
+	if err := json.Unmarshal(data, &hints); err == nil {
+		r.Hints = hints
+		return nil
+	}
+
+	return errors.New("invalid inlay hint response: not null or []InlayHint")
+}
diff --git a/inlay_hints_test.go b/inlay_hints_test.go
new file mode 100644
index 0000000..02b2fc8
--- /dev/null
+++ b/inlay_hints_test.go
@@ -0,0 +1,158 @@
+package protocol_test
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/laravel-ls/protocol"
+)
+
+func Test_InlayHint_ParamsUnmarshalValidJSON(t *testing.T) {
+	data := []byte(`{"textDocument":{"uri":"file:///tmp/main.go"},"range":{"start":{"line":1,"character":2},"end":{"line":1,"character":8}}}`)
+
+	var params protocol.InlayHintParams
+	if err := json.Unmarshal(data, &params); err != nil {
+		t.Fatalf("unmarshal InlayHintParams failed: %v", err)
+	}
+
+	if params.TextDocument.URI != "file:///tmp/main.go" {
+		t.Fatalf("unexpected textDocument URI: %q", params.TextDocument.URI)
+	}
+
+	if params.Range.Start.Line != 1 || params.Range.End.Character != 8 {
+		t.Fatalf("unexpected range: %+v", params.Range)
+	}
+}
+
+func Test_InlayHintLabel_UnmarshalString(t *testing.T) {
+	var label protocol.InlayHintLabel
+	if err := json.Unmarshal([]byte(`"x:"`), &label); err != nil {
+		t.Fatalf("unmarshal InlayHintLabel string failed: %v", err)
+	}
+
+	if label.String == nil || *label.String != "x:" {
+		t.Fatalf("expected string label 'x:', got %+v", label)
+	}
+
+	if label.Parts != nil {
+		t.Fatalf("expected parts to be nil for string label")
+	}
+}
+
+func Test_InlayHintLabel_UnmarshalParts(t *testing.T) {
+	data := []byte(`[{"value":"name"},{"value":":","tooltip":"separator"}]`)
+
+	var label protocol.InlayHintLabel
+	if err := json.Unmarshal(data, &label); err != nil {
+		t.Fatalf("unmarshal InlayHintLabel parts failed: %v", err)
+	}
+
+	if len(label.Parts) != 2 {
+		t.Fatalf("expected 2 label parts, got %d", len(label.Parts))
+	}
+
+	if label.Parts[1].Tooltip == nil || label.Parts[1].Tooltip.String == nil || *label.Parts[1].Tooltip.String != "separator" {
+		t.Fatalf("expected second part tooltip string to be set, got %+v", label.Parts[1].Tooltip)
+	}
+}
+
+func Test_InlayHintTooltip_UnmarshalMarkupContent(t *testing.T) {
+	data := []byte(`{"kind":"markdown","value":"**hint**"}`)
+
+	var tooltip protocol.InlayHintTooltip
+	if err := json.Unmarshal(data, &tooltip); err != nil {
+		t.Fatalf("unmarshal InlayHintTooltip markup failed: %v", err)
+	}
+
+	if tooltip.MarkupContent == nil || tooltip.MarkupContent.Kind != protocol.MarkupKindMarkdown {
+		t.Fatalf("expected markdown tooltip, got %+v", tooltip)
+	}
+}
+
+func Test_InlayHint_UnmarshalTypedObject(t *testing.T) {
+	data := []byte(`{
+		"position": {"line": 2, "character": 10},
+		"label": [{"value":"x"},{"value":":","tooltip":{"kind":"plaintext","value":"type separator"}}],
+		"kind": 1,
+		"textEdits": [{"range":{"start":{"line":2,"character":8},"end":{"line":2,"character":9}},"newText":"value"}],
+		"tooltip": "inferred type",
+		"paddingLeft": true,
+		"paddingRight": false,
+		"data": {"id": 42}
+	}`)
+
+	var hint protocol.InlayHint
+	if err := json.Unmarshal(data, &hint); err != nil {
+		t.Fatalf("unmarshal InlayHint failed: %v", err)
+	}
+
+	if hint.Position.Line != 2 || hint.Position.Character != 10 {
+		t.Fatalf("unexpected position: %+v", hint.Position)
+	}
+
+	if hint.Kind == nil || *hint.Kind != protocol.InlayHintKindType {
+		t.Fatalf("expected kind=InlayHintKindType, got %+v", hint.Kind)
+	}
+
+	if hint.Tooltip == nil || hint.Tooltip.String == nil || *hint.Tooltip.String != "inferred type" {
+		t.Fatalf("expected tooltip string 'inferred type', got %+v", hint.Tooltip)
+	}
+
+	if len(hint.TextEdits) != 1 {
+		t.Fatalf("expected 1 text edit, got %d", len(hint.TextEdits))
+	}
+}
+
+func Test_InlayHintResponse_UnmarshalArrayAndNull(t *testing.T) {
+	var list protocol.InlayHintResponse
+	if err := json.Unmarshal([]byte(`[{"position":{"line":0,"character":1},"label":"x:"}]`), &list); err != nil {
+		t.Fatalf("unmarshal InlayHintResponse array failed: %v", err)
+	}
+
+	if list.Null {
+		t.Fatalf("expected non-null response for array")
+	}
+
+	if len(list.Hints) != 1 {
+		t.Fatalf("expected 1 hint, got %d", len(list.Hints))
+	}
+
+	var nullRes protocol.InlayHintResponse
+	if err := json.Unmarshal([]byte(`null`), &nullRes); err != nil {
+		t.Fatalf("unmarshal InlayHintResponse null failed: %v", err)
+	}
+
+	if !nullRes.Null {
+		t.Fatalf("expected null response flag to be true")
+	}
+}
+
+func Test_InlayHintResponse_MarshalArrayAndNull(t *testing.T) {
+	response := protocol.InlayHintResponse{
+		Hints: []protocol.InlayHint{{
+			Position: protocol.Position{Line: 0, Character: 0},
+			Label: func() protocol.InlayHintLabel {
+				label := "a"
+				return protocol.InlayHintLabel{String: &label}
+			}(),
+		}},
+	}
+
+	data, err := json.Marshal(response)
+	if err != nil {
+		t.Fatalf("marshal InlayHintResponse array failed: %v", err)
+	}
+
+	if string(data) == "null" {
+		t.Fatalf("expected array JSON, got null")
+	}
+
+	nullData, err := json.Marshal(protocol.InlayHintResponse{Null: true})
+	if err != nil {
+		t.Fatalf("marshal InlayHintResponse null failed: %v", err)
+	}
+
+	if string(nullData) != "null" {
+		t.Fatalf("expected null JSON, got %s", string(nullData))
+	}
+}