diff --git a/mlir/include/mlir/TableGen/Attribute.h b/mlir/include/mlir/TableGen/Attribute.h
--- a/mlir/include/mlir/TableGen/Attribute.h
+++ b/mlir/include/mlir/TableGen/Attribute.h
@@ -113,9 +113,6 @@
 
   // Returns the dialect for the attribute if defined.
   Dialect getDialect() const;
-
-  // Returns the description of the attribute.
-  StringRef getDescription() const;
 };
 
 // Wrapper class providing helper methods for accessing MLIR constant attribute
diff --git a/mlir/include/mlir/TableGen/Constraint.h b/mlir/include/mlir/TableGen/Constraint.h
--- a/mlir/include/mlir/TableGen/Constraint.h
+++ b/mlir/include/mlir/TableGen/Constraint.h
@@ -50,10 +50,14 @@
   // mlir::Attribute.
   std::string getConditionTemplate() const;
 
-  // Returns the user-readable description of this constraint. If the
-  // description is not provided, returns the TableGen def name.
+  // Returns the user-readable summary of this constraint. If the summary is not
+  // provided, returns the TableGen def name.
   StringRef getSummary() const;
 
+  // Returns the long-form description of this constraint. If the description is
+  // not provided, returns an empty string.
+  StringRef getDescription() const;
+
   /// Returns the name of the TablGen def of this constraint. In some cases
   /// where the current def is anonymous, the name of the base def is used (e.g.
   /// `Optional<>`/`Variadic<>` type constraints).
diff --git a/mlir/include/mlir/TableGen/Type.h b/mlir/include/mlir/TableGen/Type.h
--- a/mlir/include/mlir/TableGen/Type.h
+++ b/mlir/include/mlir/TableGen/Type.h
@@ -65,9 +65,6 @@
 public:
   explicit Type(const llvm::Record *record);
 
-  // Returns the description of the type.
-  StringRef getDescription() const;
-
   // Returns the dialect for the type if defined.
   Dialect getDialect() const;
 };
diff --git a/mlir/include/mlir/Tools/PDLL/AST/Nodes.h b/mlir/include/mlir/Tools/PDLL/AST/Nodes.h
--- a/mlir/include/mlir/Tools/PDLL/AST/Nodes.h
+++ b/mlir/include/mlir/Tools/PDLL/AST/Nodes.h
@@ -635,6 +635,13 @@
   /// Provide type casting support.
   static bool classof(const Node *node);
 
+  /// Set the documentation comment for this decl.
+  void setDocComment(Context &ctx, StringRef comment);
+
+  /// Return the documentation comment attached to this decl if it has been set.
+  /// Otherwise, returns None.
+  Optional<StringRef> getDocComment() const { return docComment; }
+
 protected:
   Decl(TypeID typeID, SMRange loc, const Name *name = nullptr)
       : Node(typeID, loc), name(name) {}
@@ -643,6 +650,10 @@
   /// The name of the decl. This is optional for some decls, such as
   /// PatternDecl.
   const Name *name;
+
+  /// The documentation comment attached to this decl. Defaults to None if
+  /// the comment is unset/unknown.
+  Optional<StringRef> docComment;
 };
 
 //===----------------------------------------------------------------------===//
diff --git a/mlir/include/mlir/Tools/PDLL/Parser/Parser.h b/mlir/include/mlir/Tools/PDLL/Parser/Parser.h
--- a/mlir/include/mlir/Tools/PDLL/Parser/Parser.h
+++ b/mlir/include/mlir/Tools/PDLL/Parser/Parser.h
@@ -26,12 +26,16 @@
 class Module;
 } // namespace ast
 
-/// Parse an AST module from the main file of the given source manager. An
-/// optional code completion context may be provided to receive code completion
-/// suggestions. If a completion is hit, this method returns a failure.
+/// Parse an AST module from the main file of the given source manager.
+/// `enableDocumentation` is an optional flag that, when set, indicates that the
+/// parser should also include documentation when building the AST when
+/// possible. `codeCompleteContext` is an optional code completion context that
+/// may be provided to receive code completion suggestions. If a completion is
+/// hit, this method returns a failure.
 FailureOr<ast::Module *>
-parsePDLAST(ast::Context &ctx, llvm::SourceMgr &sourceMgr,
-            CodeCompleteContext *codeCompleteContext = nullptr);
+parsePDLLAST(ast::Context &ctx, llvm::SourceMgr &sourceMgr,
+             bool enableDocumentation = false,
+             CodeCompleteContext *codeCompleteContext = nullptr);
 } // namespace pdll
 } // namespace mlir
 
diff --git a/mlir/lib/TableGen/Attribute.cpp b/mlir/lib/TableGen/Attribute.cpp
--- a/mlir/lib/TableGen/Attribute.cpp
+++ b/mlir/lib/TableGen/Attribute.cpp
@@ -132,10 +132,6 @@
   return Dialect(nullptr);
 }
 
-StringRef Attribute::getDescription() const {
-  return def->getValueAsString("description");
-}
-
 ConstantAttr::ConstantAttr(const DefInit *init) : def(init->getDef()) {
   assert(def->isSubClassOf("ConstantAttr") &&
          "must be subclass of TableGen 'ConstantAttr' class");
diff --git a/mlir/lib/TableGen/Constraint.cpp b/mlir/lib/TableGen/Constraint.cpp
--- a/mlir/lib/TableGen/Constraint.cpp
+++ b/mlir/lib/TableGen/Constraint.cpp
@@ -57,6 +57,10 @@
   return def->getName();
 }
 
+StringRef Constraint::getDescription() const {
+  return def->getValueAsOptionalString("description").getValueOr("");
+}
+
 StringRef Constraint::getDefName() const {
   if (Optional<StringRef> baseDefName = getBaseDefName())
     return *baseDefName;
diff --git a/mlir/lib/TableGen/Type.cpp b/mlir/lib/TableGen/Type.cpp
--- a/mlir/lib/TableGen/Type.cpp
+++ b/mlir/lib/TableGen/Type.cpp
@@ -76,10 +76,6 @@
 
 Type::Type(const llvm::Record *record) : TypeConstraint(record) {}
 
-StringRef Type::getDescription() const {
-  return def->getValueAsString("description");
-}
-
 Dialect Type::getDialect() const {
   return Dialect(def->getValueAsDef("dialect"));
 }
diff --git a/mlir/lib/Tools/PDLL/AST/Nodes.cpp b/mlir/lib/Tools/PDLL/AST/Nodes.cpp
--- a/mlir/lib/Tools/PDLL/AST/Nodes.cpp
+++ b/mlir/lib/Tools/PDLL/AST/Nodes.cpp
@@ -355,6 +355,14 @@
       TypeExpr(ctx, loc, copyStringWithNull(ctx, value));
 }
 
+//===----------------------------------------------------------------------===//
+// Decl
+//===----------------------------------------------------------------------===//
+
+void Decl::setDocComment(Context &ctx, StringRef comment) {
+  docComment = comment.copy(ctx.getAllocator());
+}
+
 //===----------------------------------------------------------------------===//
 // AttrConstraintDecl
 //===----------------------------------------------------------------------===//
diff --git a/mlir/lib/Tools/PDLL/ODS/Operation.cpp b/mlir/lib/Tools/PDLL/ODS/Operation.cpp
--- a/mlir/lib/Tools/PDLL/ODS/Operation.cpp
+++ b/mlir/lib/Tools/PDLL/ODS/Operation.cpp
@@ -20,10 +20,7 @@
 Operation::Operation(StringRef name, StringRef summary, StringRef desc,
                      StringRef nativeClassName, bool supportsTypeInferrence,
                      llvm::SMLoc loc)
-    : name(name.str()), summary(summary.str()),
+    : name(name.str()), summary(summary.str()), description(desc.str()),
       nativeClassName(nativeClassName.str()),
       supportsTypeInferrence(supportsTypeInferrence),
-      location(loc, llvm::SMLoc::getFromPointer(loc.getPointer() + 1)) {
-  llvm::raw_string_ostream descOS(description);
-  raw_indented_ostream(descOS).printReindented(desc.rtrim(" \t"));
-}
+      location(loc, llvm::SMLoc::getFromPointer(loc.getPointer() + 1)) {}
diff --git a/mlir/lib/Tools/PDLL/Parser/Parser.cpp b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
--- a/mlir/lib/Tools/PDLL/Parser/Parser.cpp
+++ b/mlir/lib/Tools/PDLL/Parser/Parser.cpp
@@ -8,6 +8,7 @@
 
 #include "mlir/Tools/PDLL/Parser/Parser.h"
 #include "Lexer.h"
+#include "mlir/Support/IndentedOstream.h"
 #include "mlir/Support/LogicalResult.h"
 #include "mlir/TableGen/Argument.h"
 #include "mlir/TableGen/Attribute.h"
@@ -43,9 +44,10 @@
 class Parser {
 public:
   Parser(ast::Context &ctx, llvm::SourceMgr &sourceMgr,
-         CodeCompleteContext *codeCompleteContext)
+         bool enableDocumentation, CodeCompleteContext *codeCompleteContext)
       : ctx(ctx), lexer(sourceMgr, ctx.getDiagEngine(), codeCompleteContext),
-        curToken(lexer.lexToken()), valueTy(ast::ValueType::get(ctx)),
+        curToken(lexer.lexToken()), enableDocumentation(enableDocumentation),
+        valueTy(ast::ValueType::get(ctx)),
         valueRangeTy(ast::ValueRangeType::get(ctx)),
         typeTy(ast::TypeType::get(ctx)),
         typeRangeTy(ast::TypeRangeType::get(ctx)),
@@ -125,6 +127,27 @@
     return opName ? ctx.getODSContext().lookupOperation(*opName) : nullptr;
   }
 
+  /// Process the given documentation string, or return an empty string if
+  /// documentation isn't enabled.
+  StringRef processDoc(StringRef doc) {
+    return enableDocumentation ? doc : StringRef();
+  }
+
+  /// Process the given documentation string and format it, or return an empty
+  /// string if documentation isn't enabled.
+  std::string processAndFormatDoc(const Twine &doc) {
+    if (!enableDocumentation)
+      return "";
+    std::string docStr;
+    {
+      llvm::raw_string_ostream docOS(docStr);
+      std::string tmpDocStr = doc.str();
+      raw_indented_ostream(docOS).printReindented(
+          StringRef(tmpDocStr).rtrim(" \t"));
+    }
+    return docStr;
+  }
+
   //===--------------------------------------------------------------------===//
   // Directives
 
@@ -140,10 +163,10 @@
   /// Create a user defined native constraint for a constraint imported from
   /// ODS.
   template <typename ConstraintT>
-  ast::Decl *createODSNativePDLLConstraintDecl(StringRef name,
-                                               StringRef codeBlock, SMRange loc,
-                                               ast::Type type,
-                                               StringRef nativeType);
+  ast::Decl *
+  createODSNativePDLLConstraintDecl(StringRef name, StringRef codeBlock,
+                                    SMRange loc, ast::Type type,
+                                    StringRef nativeType, StringRef docString);
   template <typename ConstraintT>
   ast::Decl *
   createODSNativePDLLConstraintDecl(const tblgen::Constraint &constraint,
@@ -520,6 +543,10 @@
   /// The current token within the lexer.
   Token curToken;
 
+  /// A flag indicating if the parser should add documentation to AST nodes when
+  /// viable.
+  bool enableDocumentation;
+
   /// The most recently defined decl scope.
   ast::DeclScope *curDeclScope = nullptr;
   llvm::SpecificBumpPtrAllocator<ast::DeclScope> scopeAllocator;
@@ -801,9 +828,10 @@
   ods::Context &odsContext = ctx.getODSContext();
   auto addTypeConstraint = [&](const tblgen::NamedTypeConstraint &cst)
       -> const ods::TypeConstraint & {
-    return odsContext.insertTypeConstraint(cst.constraint.getUniqueDefName(),
-                                           cst.constraint.getSummary(),
-                                           cst.constraint.getCPPClassName());
+    return odsContext.insertTypeConstraint(
+        cst.constraint.getUniqueDefName(),
+        processDoc(cst.constraint.getSummary()),
+        cst.constraint.getCPPClassName());
   };
   auto convertLocToRange = [&](llvm::SMLoc loc) -> llvm::SMRange {
     return {loc, llvm::SMLoc::getFromPointer(loc.getPointer() + 1)};
@@ -821,20 +849,20 @@
     bool inserted = false;
     ods::Operation *odsOp = nullptr;
     std::tie(odsOp, inserted) = odsContext.insertOperation(
-        op.getOperationName(), op.getSummary(), op.getDescription(),
-        op.getQualCppClassName(), supportsResultTypeInferrence,
-        op.getLoc().front());
+        op.getOperationName(), processDoc(op.getSummary()),
+        processAndFormatDoc(op.getDescription()), op.getQualCppClassName(),
+        supportsResultTypeInferrence, op.getLoc().front());
 
     // Ignore operations that have already been added.
     if (!inserted)
       continue;
 
     for (const tblgen::NamedAttribute &attr : op.getAttributes()) {
-      odsOp->appendAttribute(
-          attr.name, attr.attr.isOptional(),
-          odsContext.insertAttributeConstraint(attr.attr.getUniqueDefName(),
-                                               attr.attr.getSummary(),
-                                               attr.attr.getStorageType()));
+      odsOp->appendAttribute(attr.name, attr.attr.isOptional(),
+                             odsContext.insertAttributeConstraint(
+                                 attr.attr.getUniqueDefName(),
+                                 processDoc(attr.attr.getSummary()),
+                                 attr.attr.getStorageType()));
     }
     for (const tblgen::NamedTypeConstraint &operand : op.getOperands()) {
       odsOp->appendOperand(operand.name, getLengthKind(operand),
@@ -883,26 +911,27 @@
                       cppClassName)
             .str();
 
+    std::string desc =
+        processAndFormatDoc(def->getValueAsString("description"));
     if (def->isSubClassOf("OpInterface")) {
       decls.push_back(createODSNativePDLLConstraintDecl<ast::OpConstraintDecl>(
-          name, codeBlock, loc, opTy, cppClassName));
+          name, codeBlock, loc, opTy, cppClassName, desc));
     } else if (def->isSubClassOf("AttrInterface")) {
       decls.push_back(
           createODSNativePDLLConstraintDecl<ast::AttrConstraintDecl>(
-              name, codeBlock, loc, attrTy, cppClassName));
+              name, codeBlock, loc, attrTy, cppClassName, desc));
     } else if (def->isSubClassOf("TypeInterface")) {
       decls.push_back(
           createODSNativePDLLConstraintDecl<ast::TypeConstraintDecl>(
-              name, codeBlock, loc, typeTy, cppClassName));
+              name, codeBlock, loc, typeTy, cppClassName, desc));
     }
   }
 }
 
 template <typename ConstraintT>
-ast::Decl *
-Parser::createODSNativePDLLConstraintDecl(StringRef name, StringRef codeBlock,
-                                          SMRange loc, ast::Type type,
-                                          StringRef nativeType) {
+ast::Decl *Parser::createODSNativePDLLConstraintDecl(
+    StringRef name, StringRef codeBlock, SMRange loc, ast::Type type,
+    StringRef nativeType, StringRef docString) {
   // Build the single input parameter.
   ast::DeclScope *argScope = pushDeclScope();
   auto *paramVar = ast::VariableDecl::create(
@@ -915,6 +944,7 @@
   auto *constraintDecl = ast::UserConstraintDecl::createNative(
       ctx, ast::Name::create(ctx, name, loc), paramVar,
       /*results=*/llvm::None, codeBlock, ast::TupleType::get(ctx), nativeType);
+  constraintDecl->setDocComment(ctx, docString);
   curDeclScope->add(constraintDecl);
   return constraintDecl;
 }
@@ -931,8 +961,20 @@
       "return ::mlir::success(" + constraint.getConditionTemplate() + ");",
       &fmtContext);
 
+  // If documentation was enabled, build the doc string for the generated
+  // constraint. It would be nice to do this lazily, but TableGen information is
+  // destroyed after we finish parsing the file.
+  std::string docString;
+  if (enableDocumentation) {
+    StringRef desc = constraint.getDescription();
+    docString = processAndFormatDoc(
+        constraint.getSummary() +
+        (desc.empty() ? "" : ("\n\n" + constraint.getDescription())));
+  }
+
   return createODSNativePDLLConstraintDecl<ConstraintT>(
-      constraint.getUniqueDefName(), codeBlock, loc, type, nativeType);
+      constraint.getUniqueDefName(), codeBlock, loc, type, nativeType,
+      docString);
 }
 
 //===----------------------------------------------------------------------===//
@@ -3080,8 +3122,9 @@
 //===----------------------------------------------------------------------===//
 
 FailureOr<ast::Module *>
-mlir::pdll::parsePDLAST(ast::Context &ctx, llvm::SourceMgr &sourceMgr,
-                        CodeCompleteContext *codeCompleteContext) {
-  Parser parser(ctx, sourceMgr, codeCompleteContext);
+mlir::pdll::parsePDLLAST(ast::Context &ctx, llvm::SourceMgr &sourceMgr,
+                         bool enableDocumentation,
+                         CodeCompleteContext *codeCompleteContext) {
+  Parser parser(ctx, sourceMgr, enableDocumentation, codeCompleteContext);
   return parser.parseModule();
 }
diff --git a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
--- a/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
+++ b/mlir/lib/Tools/mlir-pdll-lsp-server/PDLLServer.cpp
@@ -110,6 +110,57 @@
   return lspDiag;
 }
 
+/// Get or extract the documentation for the given decl.
+static Optional<std::string> getDocumentationFor(llvm::SourceMgr &sourceMgr,
+                                                 const ast::Decl *decl) {
+  // If the decl already had documentation set, use it.
+  if (Optional<StringRef> doc = decl->getDocComment())
+    return doc->str();
+
+  // If the decl doesn't yet have documentation, try to extract it from the
+  // source file. This is a heuristic, and isn't intended to cover every case,
+  // but should cover the most common. We essentially look for a comment
+  // preceding the decl, and if we find one, use that as the documentation.
+  SMLoc startLoc = decl->getLoc().Start;
+  if (!startLoc.isValid())
+    return llvm::None;
+  int bufferId = sourceMgr.FindBufferContainingLoc(startLoc);
+  if (bufferId == 0)
+    return llvm::None;
+  const char *bufferStart =
+      sourceMgr.getMemoryBuffer(bufferId)->getBufferStart();
+  StringRef buffer(bufferStart, startLoc.getPointer() - bufferStart);
+
+  // Pop the last line from the buffer string.
+  auto popLastLine = [&]() -> Optional<StringRef> {
+    size_t newlineOffset = buffer.find_last_of("\n");
+    if (newlineOffset == StringRef::npos)
+      return llvm::None;
+    StringRef lastLine = buffer.drop_front(newlineOffset).trim();
+    buffer = buffer.take_front(newlineOffset);
+    return lastLine;
+  };
+
+  // Try to pop the current line, which contains the decl.
+  if (!popLastLine())
+    return llvm::None;
+
+  // Try to parse a comment string from the source file.
+  SmallVector<StringRef> commentLines;
+  while (Optional<StringRef> line = popLastLine()) {
+    // Check for a comment at the beginning of the line.
+    if (!line->startswith("//"))
+      break;
+
+    // Extract the document string from the comment.
+    commentLines.push_back(line->drop_while([](char c) { return c == '/'; }));
+  }
+
+  if (commentLines.empty())
+    return llvm::None;
+  return llvm::join(llvm::reverse(commentLines), "\n");
+}
+
 //===----------------------------------------------------------------------===//
 // PDLIndex
 //===----------------------------------------------------------------------===//
@@ -278,7 +329,7 @@
                                  const SMRange &hoverRange);
   lsp::Hover buildHoverForVariable(const ast::VariableDecl *varDecl,
                                    const SMRange &hoverRange);
-  lsp::Hover buildHoverForPattern(const ast::PatternDecl *patternDecl,
+  lsp::Hover buildHoverForPattern(const ast::PatternDecl *decl,
                                   const SMRange &hoverRange);
   lsp::Hover buildHoverForCoreConstraint(const ast::CoreConstraintDecl *decl,
                                          const SMRange &hoverRange);
@@ -361,7 +412,7 @@
     if (auto lspDiag = getLspDiagnoticFromDiag(sourceMgr, diag, uri))
       diagnostics.push_back(std::move(*lspDiag));
   });
-  astModule = parsePDLAST(astContext, sourceMgr);
+  astModule = parsePDLLAST(astContext, sourceMgr, /*enableDocumentation=*/true);
 
   // Initialize the set of parsed includes.
   lsp::gatherIncludeFiles(sourceMgr, parsedIncludes);
@@ -486,23 +537,25 @@
   return hover;
 }
 
-lsp::Hover
-PDLDocument::buildHoverForPattern(const ast::PatternDecl *patternDecl,
-                                  const SMRange &hoverRange) {
+lsp::Hover PDLDocument::buildHoverForPattern(const ast::PatternDecl *decl,
+                                             const SMRange &hoverRange) {
   lsp::Hover hover(lsp::Range(sourceMgr, hoverRange));
   {
     llvm::raw_string_ostream hoverOS(hover.contents.value);
     hoverOS << "**Pattern**";
-    if (const ast::Name *name = patternDecl->getName())
+    if (const ast::Name *name = decl->getName())
       hoverOS << ": `" << name->getName() << "`";
     hoverOS << "\n***\n";
-    if (Optional<uint16_t> benefit = patternDecl->getBenefit())
+    if (Optional<uint16_t> benefit = decl->getBenefit())
       hoverOS << "Benefit: " << *benefit << "\n";
-    if (patternDecl->hasBoundedRewriteRecursion())
+    if (decl->hasBoundedRewriteRecursion())
       hoverOS << "HasBoundedRewriteRecursion\n";
     hoverOS << "RootOp: `"
-            << patternDecl->getRootRewriteStmt()->getRootOpExpr()->getType()
-            << "`\n";
+            << decl->getRootRewriteStmt()->getRootOpExpr()->getType() << "`\n";
+
+    // Format the documentation for the decl.
+    if (Optional<std::string> doc = getDocumentationFor(sourceMgr, decl))
+      hoverOS << "\n" << *doc << "\n";
   }
   return hover;
 }
@@ -552,20 +605,24 @@
     }
     ast::Type resultType = decl->getResultType();
     if (auto resultTupleTy = resultType.dyn_cast<ast::TupleType>()) {
-      if (resultTupleTy.empty())
-        return hover;
-
-      hoverOS << "Results:\n";
-      for (auto it : llvm::zip(resultTupleTy.getElementNames(),
-                               resultTupleTy.getElementTypes())) {
-        StringRef name = std::get<0>(it);
-        hoverOS << "* " << (name.empty() ? "" : (name + ": ")) << "`"
-                << std::get<1>(it) << "`\n";
+      if (!resultTupleTy.empty()) {
+        hoverOS << "Results:\n";
+        for (auto it : llvm::zip(resultTupleTy.getElementNames(),
+                                 resultTupleTy.getElementTypes())) {
+          StringRef name = std::get<0>(it);
+          hoverOS << "* " << (name.empty() ? "" : (name + ": ")) << "`"
+                  << std::get<1>(it) << "`\n";
+        }
+        hoverOS << "***\n";
       }
     } else {
       hoverOS << "Results:\n* `" << resultType << "`\n";
+      hoverOS << "***\n";
     }
-    hoverOS << "***\n";
+
+    // Format the documentation for the decl.
+    if (Optional<std::string> doc = getDocumentationFor(sourceMgr, decl))
+      hoverOS << "\n" << *doc << "\n";
   }
   return hover;
 }
@@ -619,11 +676,13 @@
 namespace {
 class LSPCodeCompleteContext : public CodeCompleteContext {
 public:
-  LSPCodeCompleteContext(SMLoc completeLoc, lsp::CompletionList &completionList,
+  LSPCodeCompleteContext(SMLoc completeLoc, llvm::SourceMgr &sourceMgr,
+                         lsp::CompletionList &completionList,
                          ods::Context &odsContext,
                          ArrayRef<std::string> includeDirs)
-      : CodeCompleteContext(completeLoc), completionList(completionList),
-        odsContext(odsContext), includeDirs(includeDirs) {}
+      : CodeCompleteContext(completeLoc), sourceMgr(sourceMgr),
+        completionList(completionList), odsContext(odsContext),
+        includeDirs(includeDirs) {}
 
   void codeCompleteTupleMemberAccess(ast::TupleType tupleType) final {
     ArrayRef<ast::Type> elementTypes = tupleType.getElementTypes();
@@ -798,6 +857,12 @@
             strOS << ") -> " << cst->getResultType();
           }
 
+          // Format the documentation for the constraint.
+          if (Optional<std::string> doc = getDocumentationFor(sourceMgr, cst)) {
+            item.documentation =
+                lsp::MarkupContent{lsp::MarkupKind::Markdown, std::move(*doc)};
+          }
+
           completionList.items.emplace_back(item);
         }
       }
@@ -921,6 +986,7 @@
   }
 
 private:
+  llvm::SourceMgr &sourceMgr;
   lsp::CompletionList &completionList;
   ods::Context &odsContext;
   ArrayRef<std::string> includeDirs;
@@ -938,11 +1004,13 @@
   // code completion context provided.
   ods::Context tmpODSContext;
   lsp::CompletionList completionList;
-  LSPCodeCompleteContext lspCompleteContext(
-      posLoc, completionList, tmpODSContext, sourceMgr.getIncludeDirs());
+  LSPCodeCompleteContext lspCompleteContext(posLoc, sourceMgr, completionList,
+                                            tmpODSContext,
+                                            sourceMgr.getIncludeDirs());
 
   ast::Context tmpContext(tmpODSContext);
-  (void)parsePDLAST(tmpContext, sourceMgr, &lspCompleteContext);
+  (void)parsePDLLAST(tmpContext, sourceMgr, /*enableDocumentation=*/true,
+                     &lspCompleteContext);
 
   return completionList;
 }
@@ -954,10 +1022,11 @@
 namespace {
 class LSPSignatureHelpContext : public CodeCompleteContext {
 public:
-  LSPSignatureHelpContext(SMLoc completeLoc, lsp::SignatureHelp &signatureHelp,
+  LSPSignatureHelpContext(SMLoc completeLoc, llvm::SourceMgr &sourceMgr,
+                          lsp::SignatureHelp &signatureHelp,
                           ods::Context &odsContext)
-      : CodeCompleteContext(completeLoc), signatureHelp(signatureHelp),
-        odsContext(odsContext) {}
+      : CodeCompleteContext(completeLoc), sourceMgr(sourceMgr),
+        signatureHelp(signatureHelp), odsContext(odsContext) {}
 
   void codeCompleteCallSignature(const ast::CallableDecl *callable,
                                  unsigned currentNumArgs) final {
@@ -978,6 +1047,11 @@
       llvm::interleaveComma(callable->getInputs(), strOS, formatParamFn);
       strOS << ") -> " << callable->getResultType();
     }
+
+    // Format the documentation for the callable.
+    if (Optional<std::string> doc = getDocumentationFor(sourceMgr, callable))
+      signatureInfo.documentation = std::move(*doc);
+
     signatureHelp.signatures.emplace_back(std::move(signatureInfo));
   }
 
@@ -1069,6 +1143,7 @@
   }
 
 private:
+  llvm::SourceMgr &sourceMgr;
   lsp::SignatureHelp &signatureHelp;
   ods::Context &odsContext;
 };
@@ -1084,10 +1159,12 @@
   // code completion context provided.
   ods::Context tmpODSContext;
   lsp::SignatureHelp signatureHelp;
-  LSPSignatureHelpContext completeContext(posLoc, signatureHelp, tmpODSContext);
+  LSPSignatureHelpContext completeContext(posLoc, sourceMgr, signatureHelp,
+                                          tmpODSContext);
 
   ast::Context tmpContext(tmpODSContext);
-  (void)parsePDLAST(tmpContext, sourceMgr, &completeContext);
+  (void)parsePDLLAST(tmpContext, sourceMgr, /*enableDocumentation=*/true,
+                     &completeContext);
 
   return signatureHelp;
 }
diff --git a/mlir/test/mlir-pdll-lsp-server/hover.test b/mlir/test/mlir-pdll-lsp-server/hover.test
--- a/mlir/test/mlir-pdll-lsp-server/hover.test
+++ b/mlir/test/mlir-pdll-lsp-server/hover.test
@@ -5,13 +5,13 @@
   "uri":"test:///foo.pdll",
   "languageId":"pdll",
   "version":1,
-  "text":"Constraint FooCst();\nRewrite FooRewrite(op: Op) -> Op;\nPattern Foo {\nlet root: Op;\nerase root;\n}\n#include \"include/included.td\"\n#include \"include/included.pdll\""
+  "text":"Constraint FooCst();\n// This is documentation for the rewriter.\n/// And even more docs.\nRewrite FooRewrite(op: Op) -> Op;\nPattern Foo {\nlet root: Op;\nerase root;\n}\n#include \"include/included.td\"\n#include \"include/included.pdll\""
 }}}
 // -----
 // Hover on a variable.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":3,"character":6}
+  "position":{"line":5,"character":6}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
@@ -23,11 +23,11 @@
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 8,
-// CHECK-NEXT:        "line": 3
+// CHECK-NEXT:        "line": 5
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 4,
-// CHECK-NEXT:        "line": 3
+// CHECK-NEXT:        "line": 5
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
@@ -35,7 +35,7 @@
 // Hover on a pattern.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":2,"character":9}
+  "position":{"line":4,"character":9}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
@@ -47,11 +47,11 @@
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 11,
-// CHECK-NEXT:        "line": 2
+// CHECK-NEXT:        "line": 4
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 8,
-// CHECK-NEXT:        "line": 2
+// CHECK-NEXT:        "line": 4
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
@@ -59,7 +59,7 @@
 // Hover on a core constraint.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":3,"character":11}
+  "position":{"line":5,"character":11}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
@@ -71,11 +71,11 @@
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 12,
-// CHECK-NEXT:        "line": 3
+// CHECK-NEXT:        "line": 5
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 10,
-// CHECK-NEXT:        "line": 3
+// CHECK-NEXT:        "line": 5
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
@@ -107,23 +107,23 @@
 // Hover on a user rewrite.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":1,"character":11}
+  "position":{"line":3,"character":11}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
 // CHECK-NEXT:  "result": {
 // CHECK-NEXT:    "contents": {
 // CHECK-NEXT:      "kind": "markdown",
-// CHECK-NEXT:      "value": "**Rewrite**: `FooRewrite`\n***\nParameters:\n* op: `Op`\n***\nResults:\n* `Op`\n***\n"
+// CHECK-NEXT:      "value": "**Rewrite**: `FooRewrite`\n***\nParameters:\n* op: `Op`\n***\nResults:\n* `Op`\n***\n\n This is documentation for the rewriter.\n And even more docs.\n"
 // CHECK-NEXT:    },
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 18,
-// CHECK-NEXT:        "line": 1
+// CHECK-NEXT:        "line": 3
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 8,
-// CHECK-NEXT:        "line": 1
+// CHECK-NEXT:        "line": 3
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
@@ -131,7 +131,7 @@
 // Hover on an include file.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":6,"character":15}
+  "position":{"line":8,"character":15}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
@@ -143,11 +143,11 @@
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 30,
-// CHECK-NEXT:        "line": 6
+// CHECK-NEXT:        "line": 8
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 9,
-// CHECK-NEXT:        "line": 6
+// CHECK-NEXT:        "line": 8
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
@@ -155,7 +155,7 @@
 // Hover on an include file.
 {"jsonrpc":"2.0","id":1,"method":"textDocument/hover","params":{
   "textDocument":{"uri":"test:///foo.pdll"},
-  "position":{"line":7,"character":15}
+  "position":{"line":9,"character":15}
 }}
 //      CHECK:  "id": 1,
 // CHECK-NEXT:  "jsonrpc": "2.0",
@@ -167,11 +167,11 @@
 // CHECK-NEXT:    "range": {
 // CHECK-NEXT:      "end": {
 // CHECK-NEXT:        "character": 32,
-// CHECK-NEXT:        "line": 7
+// CHECK-NEXT:        "line": 9
 // CHECK-NEXT:      },
 // CHECK-NEXT:      "start": {
 // CHECK-NEXT:        "character": 9,
-// CHECK-NEXT:        "line": 7
+// CHECK-NEXT:        "line": 9
 // CHECK-NEXT:      }
 // CHECK-NEXT:    }
 // CHECK-NEXT:  }
diff --git a/mlir/tools/mlir-pdll/mlir-pdll.cpp b/mlir/tools/mlir-pdll/mlir-pdll.cpp
--- a/mlir/tools/mlir-pdll/mlir-pdll.cpp
+++ b/mlir/tools/mlir-pdll/mlir-pdll.cpp
@@ -43,9 +43,14 @@
   sourceMgr.setIncludeDirs(includeDirs);
   sourceMgr.AddNewSourceBuffer(std::move(chunkBuffer), SMLoc());
 
+  // If we are dumping ODS information, also enable documentation to ensure the
+  // summary and description information is imported as well.
+  bool enableDocumentation = dumpODS;
+
   ods::Context odsContext;
   ast::Context astContext(odsContext);
-  FailureOr<ast::Module *> module = parsePDLAST(astContext, sourceMgr);
+  FailureOr<ast::Module *> module =
+      parsePDLLAST(astContext, sourceMgr, enableDocumentation);
   if (failed(module))
     return failure();