diff --git a/pkgs/development/compilers/llvm/12/clang/default.nix b/pkgs/development/compilers/llvm/12/clang/default.nix
index 169f2f27306e..ab329e3d85d7 100644
--- a/pkgs/development/compilers/llvm/12/clang/default.nix
+++ b/pkgs/development/compilers/llvm/12/clang/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, fetch, cmake, libxml2, llvm, version, clang-tools-extra_src, python3, lld
+{ lib, stdenv, llvm_meta, fetch, cmake, libxml2, llvm, version, clang-tools-extra_src, python3, lld
 , fixDarwinDylibNames
 , enableManpages ? false
 }:
@@ -82,11 +82,20 @@ let
       inherit llvm;
     };
 
-    meta = {
-      description = "A c, c++, objective-c, and objective-c++ frontend for the llvm compiler";
-      homepage    = "https://llvm.org/";
-      license     = lib.licenses.ncsa;
-      platforms   = lib.platforms.all;
+    meta = llvm_meta // {
+      homepage = "https://clang.llvm.org/";
+      description = "A C language family frontend for LLVM";
+      longDescription = ''
+        The Clang project provides a language front-end and tooling
+        infrastructure for languages in the C language family (C, C++, Objective
+        C/C++, OpenCL, CUDA, and RenderScript) for the LLVM project.
+        It aims to deliver amazingly fast compiles, extremely useful error and
+        warning messages and to provide a platform for building great source
+        level tools. The Clang Static Analyzer and clang-tidy are tools that
+        automatically find bugs in your code, and are great examples of the sort
+        of tools that can be built using the Clang frontend as a library to
+        parse C/C++ code.
+      '';
     };
   } // lib.optionalAttrs enableManpages {
     pname = "clang-manpages";
@@ -105,6 +114,8 @@ let
 
     doCheck = false;
 
-    meta.description = "man page for Clang ${version}";
+    meta = llvm_meta // {
+      description = "man page for Clang ${version}";
+    };
   });
 in self
diff --git a/pkgs/development/compilers/llvm/12/compiler-rt/default.nix b/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
index e4c2295a0d7e..bf7f4bc4312a 100644
--- a/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/12/compiler-rt/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, version, fetch, cmake, python3, llvm, libcxxabi }:
+{ lib, stdenv, llvm_meta, version, fetch, cmake, python3, llvm, libcxxabi }:
 
 let
 
@@ -87,4 +87,19 @@ stdenv.mkDerivation rec {
     ln -s $out/lib/*/clang_rt.crtend_shared-*.o $out/lib/crtendS.o
   '';
 
+  meta = llvm_meta // {
+    homepage = "https://compiler-rt.llvm.org/";
+    description = "Compiler runtime libraries";
+    longDescription = ''
+      The compiler-rt project provides highly tuned implementations of the
+      low-level code generator support routines like "__fixunsdfdi" and other
+      calls generated when a target doesn't have a short sequence of native
+      instructions to implement a core IR operation. It also provides
+      implementations of run-time libraries for dynamic testing tools such as
+      AddressSanitizer, ThreadSanitizer, MemorySanitizer, and DataFlowSanitizer.
+    '';
+    # "All of the code in the compiler-rt project is dual licensed under the MIT
+    # license and the UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+  };
 }
diff --git a/pkgs/development/compilers/llvm/12/default.nix b/pkgs/development/compilers/llvm/12/default.nix
index c3e9cc5b4996..00922ed96e2c 100644
--- a/pkgs/development/compilers/llvm/12/default.nix
+++ b/pkgs/development/compilers/llvm/12/default.nix
@@ -20,6 +20,12 @@ let
 
   clang-tools-extra_src = fetch "clang-tools-extra" "0p3dzr0qa7mar83y66xa5m5apynf6ia0lsdsq6axwnm64ysy0hdd";
 
+  llvm_meta = {
+    license     = lib.licenses.ncsa;
+    maintainers = with lib.maintainers; [ lovek323 raskin dtzWill primeos ];
+    platforms   = lib.platforms.all;
+  };
+
   tools = lib.makeExtensible (tools: let
     callPackage = newScope (tools // { inherit stdenv cmake libxml2 python3 isl release_version version fetch; });
     mkExtraBuildCommands = cc: ''
@@ -30,13 +36,16 @@ let
       ln -s "${targetLlvmLibraries.compiler-rt.out}/share" "$rsrc/share"
       echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
     '';
+
   in {
 
-    llvm = callPackage ./llvm { };
+    llvm = callPackage ./llvm {
+      inherit llvm_meta;
+    };
 
     clang-unwrapped = callPackage ./clang {
       inherit (tools) lld;
-      inherit clang-tools-extra_src;
+      inherit clang-tools-extra_src llvm_meta;
     };
 
     # disabled until recommonmark supports sphinx 3
@@ -81,10 +90,12 @@ let
     };
 
     lld = callPackage ./lld {
+      inherit llvm_meta;
       libunwind = libraries.libunwind;
     };
 
     lldb = callPackage ./lldb {
+      inherit llvm_meta;
       inherit (darwin) libobjc bootstrap_cmds;
       inherit (darwin.apple_sdk.libs) xpc;
       inherit (darwin.apple_sdk.frameworks) Foundation Carbon Cocoa;
@@ -172,7 +183,7 @@ let
     callPackage = newScope (libraries // buildLlvmTools // { inherit stdenv cmake libxml2 python3 isl release_version version fetch; });
   in {
 
-    compiler-rt = callPackage ./compiler-rt ({} //
+    compiler-rt = callPackage ./compiler-rt ({ inherit llvm_meta; } //
       (lib.optionalAttrs (stdenv.hostPlatform.useLLVM or false) {
         stdenv = overrideCC stdenv buildLlvmTools.lldClangNoCompilerRt;
       }));
@@ -181,20 +192,20 @@ let
 
     libcxxStdenv = overrideCC stdenv buildLlvmTools.libcxxClang;
 
-    libcxx = callPackage ./libc++ ({} //
+    libcxx = callPackage ./libc++ ({ inherit llvm_meta; } //
       (lib.optionalAttrs (stdenv.hostPlatform.useLLVM or false) {
         stdenv = overrideCC stdenv buildLlvmTools.lldClangNoLibcxx;
       }));
 
-    libcxxabi = callPackage ./libc++abi ({} //
+    libcxxabi = callPackage ./libc++abi ({ inherit llvm_meta; } //
       (lib.optionalAttrs (stdenv.hostPlatform.useLLVM or false) {
         stdenv = overrideCC stdenv buildLlvmTools.lldClangNoLibcxx;
         libunwind = libraries.libunwind;
       }));
 
-    openmp = callPackage ./openmp.nix {};
+    openmp = callPackage ./openmp.nix { inherit llvm_meta; };
 
-    libunwind = callPackage ./libunwind ({} //
+    libunwind = callPackage ./libunwind ({ inherit llvm_meta; } //
       (lib.optionalAttrs (stdenv.hostPlatform.useLLVM or false) {
         stdenv = overrideCC stdenv buildLlvmTools.lldClangNoLibcxx;
       }));
diff --git a/pkgs/development/compilers/llvm/12/libc++/default.nix b/pkgs/development/compilers/llvm/12/libc++/default.nix
index ef845e0f7b03..d85d890879ec 100644
--- a/pkgs/development/compilers/llvm/12/libc++/default.nix
+++ b/pkgs/development/compilers/llvm/12/libc++/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, fetch, fetchpatch, cmake, python3, libcxxabi, llvm, fixDarwinDylibNames, version
+{ lib, stdenv, llvm_meta, fetch, cmake, python3, libcxxabi, llvm, fixDarwinDylibNames, version
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
 
@@ -40,10 +40,15 @@ stdenv.mkDerivation {
     isLLVM = true;
   };
 
-  meta = {
+  meta = llvm_meta // {
     homepage = "https://libcxx.llvm.org/";
-    description = "A new implementation of the C++ standard library, targeting C++11";
-    license = with lib.licenses; [ ncsa mit ];
-    platforms = lib.platforms.all;
+    description = "C++ standard library";
+    longDescription = ''
+      libc++ is an implementation of the C++ standard library, targeting C++11,
+      C++14 and above.
+    '';
+    # "All of the code in libc++ is dual licensed under the MIT license and the
+    # UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
   };
 }
diff --git a/pkgs/development/compilers/llvm/12/libc++abi/default.nix b/pkgs/development/compilers/llvm/12/libc++abi/default.nix
index 6aff78727531..22ec211a3b05 100644
--- a/pkgs/development/compilers/llvm/12/libc++abi/default.nix
+++ b/pkgs/development/compilers/llvm/12/libc++abi/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, cmake, python3, fetch, libcxx, libunwind, llvm, version
+{ lib, stdenv, llvm_meta, cmake, python3, fetch, libcxx, libunwind, llvm, version
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
 
@@ -57,11 +57,15 @@ stdenv.mkDerivation {
       ln -s libc++abi.so.1.0 $out/lib/libc++abi.so.1
     '';
 
-  meta = {
+  meta = llvm_meta // {
     homepage = "https://libcxxabi.llvm.org/";
-    description = "A new implementation of low level support for a standard C++ library";
-    license = with lib.licenses; [ ncsa mit ];
-    maintainers = with lib.maintainers; [ vlstill ];
-    platforms = lib.platforms.all;
+    description = "Provides C++ standard library support";
+    longDescription = ''
+      libc++abi is a new implementation of low level support for a standard C++ library.
+    '';
+    # "All of the code in libc++abi is dual licensed under the MIT license and
+    # the UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+    maintainers = llvm_meta.maintainers ++ [ lib.maintainers.vlstill ];
   };
 }
diff --git a/pkgs/development/compilers/llvm/12/libunwind/default.nix b/pkgs/development/compilers/llvm/12/libunwind/default.nix
index 56ee98176d2d..8b75146d7b22 100644
--- a/pkgs/development/compilers/llvm/12/libunwind/default.nix
+++ b/pkgs/development/compilers/llvm/12/libunwind/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, version, fetch, libcxx, llvm, cmake
+{ lib, stdenv, llvm_meta, version, fetch, libcxx, llvm, cmake
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
 
@@ -18,4 +18,16 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake ];
 
   cmakeFlags = lib.optional (!enableShared) "-DLIBUNWIND_ENABLE_SHARED=OFF";
+
+  meta = llvm_meta // {
+    # Details: https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst
+    homepage = "https://clang.llvm.org/docs/Toolchain.html#unwind-library";
+    description = "LLVM's unwinder library";
+    longDescription = ''
+      The unwind library provides a family of _Unwind_* functions implementing
+      the language-neutral stack unwinding portion of the Itanium C++ ABI (Level
+      I). It is a dependency of the C++ ABI library, and sometimes is a
+      dependency of other runtimes.
+    '';
+  };
 }
diff --git a/pkgs/development/compilers/llvm/12/lld/default.nix b/pkgs/development/compilers/llvm/12/lld/default.nix
index 1d983f13c0f1..18b72a904071 100644
--- a/pkgs/development/compilers/llvm/12/lld/default.nix
+++ b/pkgs/development/compilers/llvm/12/lld/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv
+{ lib, stdenv, llvm_meta
 , fetch
 , libunwind
 , cmake
@@ -30,10 +30,16 @@ stdenv.mkDerivation rec {
     moveToOutput lib "$dev"
   '';
 
-  meta = {
-    description = "The LLVM Linker";
-    homepage    = "https://lld.llvm.org/";
-    license     = lib.licenses.ncsa;
-    platforms   = lib.platforms.all;
+  meta = llvm_meta // {
+    homepage = "https://lld.llvm.org/";
+    description = "The LLVM linker";
+    longDescription = ''
+      LLD is a linker from the LLVM project that is a drop-in replacement for
+      system linkers and runs much faster than them. It also provides features
+      that are useful for toolchain developers.
+      The linker supports ELF (Unix), PE/COFF (Windows), Mach-O (macOS) and
+      WebAssembly in descending order of completeness. Internally, LLD consists
+      of several different linkers.
+    '';
   };
 }
diff --git a/pkgs/development/compilers/llvm/12/lldb/default.nix b/pkgs/development/compilers/llvm/12/lldb/default.nix
index 7996487a2a89..1fce82d7990e 100644
--- a/pkgs/development/compilers/llvm/12/lldb/default.nix
+++ b/pkgs/development/compilers/llvm/12/lldb/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv
+{ lib, stdenv, llvm_meta
 , fetch
 , cmake
 , zlib
@@ -72,11 +72,15 @@ stdenv.mkDerivation (rec {
     ln -s $out/bin/lldb-vscode $out/share/vscode/extensions/llvm-org.lldb-vscode-0.1.0/bin
   '';
 
-  meta = with lib; {
+  meta = llvm_meta // {
+    homepage = "https://lldb.llvm.org/";
     description = "A next-generation high-performance debugger";
-    homepage = "https://lldb.llvm.org";
-    license = licenses.ncsa;
-    platforms = platforms.all;
+    longDescription = ''
+      LLDB is a next generation, high-performance debugger. It is built as a set
+      of reusable components which highly leverage existing libraries in the
+      larger LLVM Project, such as the Clang expression parser and LLVM
+      disassembler.
+    '';
   };
 } // lib.optionalAttrs enableManpages {
   pname = "lldb-manpages";
@@ -99,5 +103,7 @@ stdenv.mkDerivation (rec {
 
   doCheck = false;
 
-  meta.description = "man pages for LLDB ${version}";
+  meta = llvm_meta // {
+    description = "man pages for LLDB ${version}";
+  };
 })
diff --git a/pkgs/development/compilers/llvm/12/llvm/default.nix b/pkgs/development/compilers/llvm/12/llvm/default.nix
index 351b5b879404..0d0075fddc79 100644
--- a/pkgs/development/compilers/llvm/12/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/12/llvm/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv
+{ lib, stdenv, llvm_meta
 , fetch
 , cmake
 , python3
@@ -160,12 +160,23 @@ in stdenv.mkDerivation (rec {
   checkTarget = "check-all";
 
   requiredSystemFeatures = [ "big-parallel" ];
-  meta = {
-    description = "Collection of modular and reusable compiler and toolchain technologies";
-    homepage    = "https://llvm.org/";
-    license     = lib.licenses.ncsa;
-    maintainers = with lib.maintainers; [ lovek323 raskin dtzWill primeos ];
-    platforms   = lib.platforms.all;
+  meta = llvm_meta // {
+    homepage = "https://llvm.org/";
+    description = "A collection of modular and reusable compiler and toolchain technologies";
+    longDescription = ''
+      The LLVM Project is a collection of modular and reusable compiler and
+      toolchain technologies. Despite its name, LLVM has little to do with
+      traditional virtual machines. The name "LLVM" itself is not an acronym; it
+      is the full name of the project.
+      LLVM began as a research project at the University of Illinois, with the
+      goal of providing a modern, SSA-based compilation strategy capable of
+      supporting both static and dynamic compilation of arbitrary programming
+      languages. Since then, LLVM has grown to be an umbrella project consisting
+      of a number of subprojects, many of which are being used in production by
+      a wide variety of commercial and open source projects as well as being
+      widely used in academic research. Code in the LLVM project is licensed
+      under the "Apache 2.0 License with LLVM exceptions".
+    '';
   };
 } // lib.optionalAttrs enableManpages {
   pname = "llvm-manpages";
@@ -185,5 +196,7 @@ in stdenv.mkDerivation (rec {
 
   doCheck = false;
 
-  meta.description = "man pages for LLVM ${version}";
+  meta = llvm_meta // {
+    description = "man pages for LLVM ${version}";
+  };
 })
diff --git a/pkgs/development/compilers/llvm/12/openmp.nix b/pkgs/development/compilers/llvm/12/openmp.nix
index 07c1c2b0aedf..c107258dd189 100644
--- a/pkgs/development/compilers/llvm/12/openmp.nix
+++ b/pkgs/development/compilers/llvm/12/openmp.nix
@@ -1,5 +1,6 @@
 { lib
 , stdenv
+, llvm_meta
 , fetch
 , cmake
 , llvm
@@ -16,10 +17,18 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ cmake perl ];
   buildInputs = [ llvm ];
 
-  meta = {
-    description = "Components required to build an executable OpenMP program";
-    homepage    = "https://openmp.llvm.org/";
-    license     = lib.licenses.mit;
-    platforms   = lib.platforms.all;
+  meta = llvm_meta // {
+    homepage = "https://openmp.llvm.org/";
+    description = "Support for the OpenMP language";
+    longDescription = ''
+      The OpenMP subproject of LLVM contains the components required to build an
+      executable OpenMP program that are outside the compiler itself.
+      Contains the code for the runtime library against which code compiled by
+      "clang -fopenmp" must be linked before it can run and the library that
+      supports offload to target devices.
+    '';
+    # "All of the code is dual licensed under the MIT license and the UIUC
+    # License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
   };
 }