diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -1375,7 +1375,7 @@
   /// descendants. If not defined, the children have not been resolved.
   llvm::Optional<std::vector<TypeHierarchyItem>> children;
 
-  /// An optional 'data' filed, which can be used to identify a type hierarchy
+  /// An optional 'data' field, which can be used to identify a type hierarchy
   /// item in a resolve request.
   llvm::Optional<std::string> data;
 };
@@ -1397,6 +1397,83 @@
 bool fromJSON(const llvm::json::Value &, ResolveTypeHierarchyItemParams &,
               llvm::json::Path);
 
+enum class SymbolTag { Deprecated = 1 };
+llvm::json::Value toJSON(SymbolTag);
+
+/// The parameter of a `textDocument/prepareCallHierarchy` request.
+struct CallHierarchyPrepareParams : public TextDocumentPositionParams {};
+
+/// Represents programming constructs like functions or constructors
+/// in the context of call hierarchy.
+struct CallHierarchyItem {
+  /// The name of this item.
+  std::string name;
+
+  /// The kind of this item.
+  SymbolKind kind;
+
+  /// Tags for this item.
+  std::vector<SymbolTag> tags;
+
+  /// More detaill for this item, e.g. the signature of a function.
+  std::string detail;
+
+  /// The resource identifier of this item.
+  URIForFile uri;
+
+  /// The range enclosing this symbol not including leading / trailing
+  /// whitespace but everything else, e.g. comments and code.
+  Range range;
+
+  /// The range that should be selected and revealed when this symbol
+  /// is being picked, e.g. the name of a function.
+  /// Must be contained by `Rng`.
+  Range selectionRange;
+
+  /// An optional 'data' field, which can be used to identify a call
+  /// hierarchy item in an incomingCalls or outgoingCalls request.
+  std::string data;
+};
+llvm::json::Value toJSON(const CallHierarchyItem &);
+bool fromJSON(const llvm::json::Value &, CallHierarchyItem &, llvm::json::Path);
+
+/// The parameter of a `callHierarchy/incomingCalls` request.
+struct CallHierarchyIncomingCallsParams {
+  CallHierarchyItem item;
+};
+bool fromJSON(const llvm::json::Value &, CallHierarchyIncomingCallsParams &,
+              llvm::json::Path);
+
+/// Represents an incoming call, e.g. a caller of a method or constructor.
+struct CallHierarchyIncomingCall {
+  /// The item that makes the call.
+  CallHierarchyItem from;
+
+  /// The range at which the calls appear.
+  /// This is relative to the caller denoted by `From`.
+  std::vector<Range> fromRanges;
+};
+llvm::json::Value toJSON(const CallHierarchyIncomingCall &);
+
+/// The parameter of a `callHierarchy/outgoingCalls` request.
+struct CallHierarchyOutgoingCallsParams {
+  CallHierarchyItem item;
+};
+bool fromJSON(const llvm::json::Value &, CallHierarchyOutgoingCallsParams &,
+              llvm::json::Path);
+
+/// Represents an outgoing call, e.g. calling a getter from a method or
+/// a method from a constructor etc.
+struct CallHierarchyOutgoingCall {
+  /// The item that is called.
+  CallHierarchyItem to;
+
+  /// The range at which this item is called.
+  /// This is the range relative to the caller, and not `To`.
+  std::vector<Range> fromRanges;
+};
+llvm::json::Value toJSON(const CallHierarchyOutgoingCall &);
+
 struct ReferenceParams : public TextDocumentPositionParams {
   // For now, no options like context.includeDeclaration are supported.
 };
diff --git a/clang-tools-extra/clangd/Protocol.cpp b/clang-tools-extra/clangd/Protocol.cpp
--- a/clang-tools-extra/clangd/Protocol.cpp
+++ b/clang-tools-extra/clangd/Protocol.cpp
@@ -1209,6 +1209,58 @@
   return fromJSON(Params, Base, P);
 }
 
+llvm::json::Value toJSON(SymbolTag Tag) {
+  return llvm::json::Value{static_cast<int>(Tag)};
+}
+
+llvm::json::Value toJSON(const CallHierarchyItem &I) {
+  llvm::json::Object Result{{"name", I.name},
+                            {"kind", static_cast<int>(I.kind)},
+                            {"range", I.range},
+                            {"selectionRange", I.selectionRange},
+                            {"uri", I.uri}};
+  if (!I.tags.empty())
+    Result["tags"] = I.tags;
+  if (!I.detail.empty())
+    Result["detail"] = I.detail;
+  if (!I.data.empty())
+    Result["data"] = I.data;
+  return std::move(Result);
+}
+
+bool fromJSON(const llvm::json::Value &Params, CallHierarchyItem &I,
+              llvm::json::Path P) {
+  llvm::json::ObjectMapper O(Params, P);
+
+  // Populate the required fields only. We don't care about the
+  // optional fields `Tags` and `Detail` for the purpose of
+  // client --> server communication.
+  return O && O.map("name", I.name) && O.map("kind", I.kind) &&
+         O.map("uri", I.uri) && O.map("range", I.range) &&
+         O.map("selectionRange", I.selectionRange) &&
+         O.mapOptional("data", I.data);
+}
+
+bool fromJSON(const llvm::json::Value &Params,
+              CallHierarchyIncomingCallsParams &C, llvm::json::Path P) {
+  llvm::json::ObjectMapper O(Params, P);
+  return O.map("item", C.item);
+}
+
+llvm::json::Value toJSON(const CallHierarchyIncomingCall &C) {
+  return llvm::json::Object{{"from", C.from}, {"fromRanges", C.fromRanges}};
+}
+
+bool fromJSON(const llvm::json::Value &Params,
+              CallHierarchyOutgoingCallsParams &C, llvm::json::Path P) {
+  llvm::json::ObjectMapper O(Params, P);
+  return O.map("item", C.item);
+}
+
+llvm::json::Value toJSON(const CallHierarchyOutgoingCall &C) {
+  return llvm::json::Object{{"to", C.to}, {"fromRanges", C.fromRanges}};
+}
+
 static const char *toString(OffsetEncoding OE) {
   switch (OE) {
   case OffsetEncoding::UTF8: