diff --git a/src/applications/search/compiler/PhutilSearchQueryCompiler.php b/src/applications/search/compiler/PhutilSearchQueryCompiler.php
--- a/src/applications/search/compiler/PhutilSearchQueryCompiler.php
+++ b/src/applications/search/compiler/PhutilSearchQueryCompiler.php
@@ -29,19 +29,32 @@
     return $this;
   }
 
+  /**
+   * @return PhutilSearchStemmer
+   */
   public function getStemmer() {
     return $this->stemmer;
   }
 
+  /**
+   * @param bool
+   */
   public function setEnableFunctions($enable_functions) {
     $this->enableFunctions = $enable_functions;
     return $this;
   }
 
+  /**
+   * @return bool
+   */
   public function getEnableFunctions() {
     return $this->enableFunctions;
   }
 
+  /**
+   * @param array<PhutilSearchQueryToken> $tokens
+   * @return string|null
+   */
   public function compileQuery(array $tokens) {
     assert_instances_of($tokens, 'PhutilSearchQueryToken');
 
@@ -53,6 +66,10 @@
     return $this->compileRenderedTokens($result);
   }
 
+  /**
+   * @param array<PhutilSearchQueryToken> $tokens
+   * @return string|null
+   */
   public function compileLiteralQuery(array $tokens) {
     assert_instances_of($tokens, 'PhutilSearchQueryToken');
 
@@ -67,6 +84,10 @@
     return $this->compileRenderedTokens($result);
   }
 
+  /**
+   * @param array<PhutilSearchQueryToken> $tokens
+   * @return string|null
+   */
   public function compileStemmedQuery(array $tokens) {
     assert_instances_of($tokens, 'PhutilSearchQueryToken');
 
@@ -81,6 +102,9 @@
     return $this->compileRenderedTokens($result);
   }
 
+  /**
+   * @return string|null
+   */
   private function compileRenderedTokens(array $list) {
     if (!$list) {
       return null;
@@ -90,6 +114,9 @@
     return implode(' ', $list);
   }
 
+  /**
+   * @return PhutilSearchQueryToken[]
+   */
   public function newTokens($query) {
     $results = $this->tokenizeQuery($query);
 
@@ -101,6 +128,12 @@
     return $tokens;
   }
 
+  /**
+   * @param  string $query Search string or part of the search string
+   * @return array<string[]> An array consisting of array elements like
+   *   {"operator":"and","quoted":false,"value":"get","raw":"get",
+   *   "function":null}
+   */
   private function tokenizeQuery($query) {
     $maximum_bytes = 1024;
     if ($query === null) {
diff --git a/src/applications/search/compiler/PhutilSearchQueryToken.php b/src/applications/search/compiler/PhutilSearchQueryToken.php
--- a/src/applications/search/compiler/PhutilSearchQueryToken.php
+++ b/src/applications/search/compiler/PhutilSearchQueryToken.php
@@ -7,6 +7,9 @@
   private $operator;
   private $function;
 
+  /**
+   * @return PhutilSearchQueryToken
+   */
   public static function newFromDictionary(array $dictionary) {
     $token = new self();
 
diff --git a/src/applications/search/compiler/PhutilSearchStemmer.php b/src/applications/search/compiler/PhutilSearchStemmer.php
--- a/src/applications/search/compiler/PhutilSearchStemmer.php
+++ b/src/applications/search/compiler/PhutilSearchStemmer.php
@@ -3,11 +3,22 @@
 final class PhutilSearchStemmer
   extends Phobject {
 
+  /**
+   * Perform normalization and stemming on input token
+   * @param  string $token Input token
+   * @return string Either stemmed token, or original input if token is too
+   *   short (<3 characters) or if token contains certain punctuation elements
+   */
   public function stemToken($token) {
     $token = $this->normalizeToken($token);
     return $this->applyStemmer($token);
   }
 
+  /**
+   * Perform normalization and stemming on input corpus
+   * @param  string $corpus Input corpus
+   * @return string Stemmed corpus
+   */
   public function stemCorpus($corpus) {
     $corpus = $this->normalizeCorpus($corpus);
     $tokens = preg_split('/[^a-zA-Z0-9\x7F-\xFF._]+/', $corpus);
@@ -31,15 +42,29 @@
     return implode(' ', $stems);
   }
 
+  /**
+   * Internally convert token to lower case in a UTF8-aware way.
+   * @param   string  $token Input token.
+   * @return  string  Input token, in some semblance of lower case.
+   */
   private function normalizeToken($token) {
     return phutil_utf8_strtolower($token);
   }
 
+  /**
+   * Internally convert corpus to lower case in a UTF8-aware way.
+   * @param   string  $corpus Input corpus.
+   * @return  string  Input corpus, in some semblance of lower case.
+   */
   private function normalizeCorpus($corpus) {
     return phutil_utf8_strtolower($corpus);
   }
 
   /**
+   * Internally pass normalized tokens to Porter to perform stemming. Or not.
+   * @param  string $normalized_token Lower case token
+   * @return string Either stemmed token, or original input if token is too
+   *   short (<3 characters) or if token contains certain punctuation elements
    * @phutil-external-symbol class Porter
    */
   private function applyStemmer($normalized_token) {
diff --git a/src/applications/search/fulltextstorage/PhabricatorFerretFulltextStorageEngine.php b/src/applications/search/fulltextstorage/PhabricatorFerretFulltextStorageEngine.php
--- a/src/applications/search/fulltextstorage/PhabricatorFerretFulltextStorageEngine.php
+++ b/src/applications/search/fulltextstorage/PhabricatorFerretFulltextStorageEngine.php
@@ -6,6 +6,9 @@
   private $fulltextTokens = array();
   private $engineLimits;
 
+  /**
+   * @return string Engine identifier string: "mysql"
+   */
   public function getEngineIdentifier() {
     return 'mysql';
   }
diff --git a/src/applications/search/query/PhabricatorFulltextResultSet.php b/src/applications/search/query/PhabricatorFulltextResultSet.php
--- a/src/applications/search/query/PhabricatorFulltextResultSet.php
+++ b/src/applications/search/query/PhabricatorFulltextResultSet.php
@@ -14,11 +14,17 @@
     return $this->phids;
   }
 
+  /**
+   * @param array<PhabricatorFulltextToken>
+   */
   public function setFulltextTokens($fulltext_tokens) {
     $this->fulltextTokens = $fulltext_tokens;
     return $this;
   }
 
+  /**
+   * @return array<PhabricatorFulltextToken>
+   */
   public function getFulltextTokens() {
     return $this->fulltextTokens;
   }
diff --git a/src/applications/search/query/PhabricatorFulltextToken.php b/src/applications/search/query/PhabricatorFulltextToken.php
--- a/src/applications/search/query/PhabricatorFulltextToken.php
+++ b/src/applications/search/query/PhabricatorFulltextToken.php
@@ -11,6 +11,9 @@
     return $this;
   }
 
+  /**
+   * @return PhutilSearchQueryToken
+   */
   public function getToken() {
     return $this->token;
   }
diff --git a/src/applications/search/query/PhabricatorSearchDocumentQuery.php b/src/applications/search/query/PhabricatorSearchDocumentQuery.php
--- a/src/applications/search/query/PhabricatorSearchDocumentQuery.php
+++ b/src/applications/search/query/PhabricatorSearchDocumentQuery.php
@@ -26,6 +26,9 @@
     return $this->getRequiredCapabilities();
   }
 
+  /**
+   * @return PhabricatorFulltextResultSet
+   */
   public function getFulltextResultSet() {
     if (!$this->fulltextResultSet) {
       throw new PhutilInvalidStateException('execute');
@@ -39,6 +42,11 @@
     $this->fulltextResultSet = null;
   }
 
+  /**
+   * Load a raw page of results.
+   *
+   * @return list PHIDs of the search result objects as array keys.
+   */
   protected function loadPage() {
     // NOTE: The offset and limit information in the inherited properties of
     // this object represent a policy-filtered offset and limit, but the
diff --git a/src/infrastructure/cluster/search/PhabricatorElasticsearchHost.php b/src/infrastructure/cluster/search/PhabricatorElasticsearchHost.php
--- a/src/infrastructure/cluster/search/PhabricatorElasticsearchHost.php
+++ b/src/infrastructure/cluster/search/PhabricatorElasticsearchHost.php
@@ -20,10 +20,16 @@
     return $this;
   }
 
+  /**
+   * @return string Display name of the search host: "Elasticsearch"
+   */
   public function getDisplayName() {
     return pht('Elasticsearch');
   }
 
+  /**
+   * @return string[] Get a list of fields to show in the status overview UI
+   */
   public function getStatusViewColumns() {
     return array(
         pht('Protocol') => $this->getProtocol(),
@@ -40,6 +46,9 @@
     return $this;
   }
 
+  /**
+   * @return string Search host protocol, by default "http"
+   */
   public function getProtocol() {
     return $this->protocol;
   }
@@ -62,6 +71,9 @@
     return $this->version;
   }
 
+  /**
+   * @return PhutilURI
+   */
   public function getURI($to_path = null) {
     $uri = id(new PhutilURI('http://'.$this->getHost()))
       ->setProtocol($this->getProtocol())
diff --git a/src/infrastructure/cluster/search/PhabricatorMySQLSearchHost.php b/src/infrastructure/cluster/search/PhabricatorMySQLSearchHost.php
--- a/src/infrastructure/cluster/search/PhabricatorMySQLSearchHost.php
+++ b/src/infrastructure/cluster/search/PhabricatorMySQLSearchHost.php
@@ -9,10 +9,16 @@
     return $this;
   }
 
+  /**
+   * @return string Display name of the search host: "MySQL"
+   */
   public function getDisplayName() {
     return 'MySQL';
   }
 
+  /**
+   * @return string[] Get a list of fields to show in the status overview UI
+   */
   public function getStatusViewColumns() {
     return array(
         pht('Protocol') => 'mysql',
@@ -20,6 +26,9 @@
     );
   }
 
+  /**
+   * @return string Search host protocol: "mysql"
+   */
   public function getProtocol() {
     return 'mysql';
   }
diff --git a/src/infrastructure/cluster/search/PhabricatorSearchService.php b/src/infrastructure/cluster/search/PhabricatorSearchService.php
--- a/src/infrastructure/cluster/search/PhabricatorSearchService.php
+++ b/src/infrastructure/cluster/search/PhabricatorSearchService.php
@@ -26,6 +26,8 @@
 
   /**
    * @throws Exception
+   * @return PhabricatorSearchHost An instance of a subclass of
+   *   PhabricatorSearchHost
    */
   public function newHost($config) {
     $host = clone($this->hostType);
@@ -35,14 +37,24 @@
     return $host;
   }
 
+  /**
+   * @return PhabricatorFulltextStorageEngine A subclass of
+   *   PhabricatorFulltextStorageEngine
+   */
   public function getEngine() {
     return $this->engine;
   }
 
+  /**
+   * @return string Display name of the search host, e.g. "MySQL"
+   */
   public function getDisplayName() {
     return $this->hostType->getDisplayName();
   }
 
+  /**
+   * @return string[] Get a list of fields to show in the status overview UI
+   */
   public function getStatusViewColumns() {
     return $this->hostType->getStatusViewColumns();
   }
@@ -66,6 +78,9 @@
 
   }
 
+  /**
+   * @return string[]
+   */
   public function getConfig() {
     return $this->config;
   }
@@ -249,6 +264,10 @@
     return $result_set->getPHIDs();
   }
 
+  /**
+   * @param  PhabricatorSavedQuery $query
+   * @return PhabricatorFulltextResultSet
+   */
   public static function newResultSet(PhabricatorSavedQuery $query) {
     $exceptions = array();
     // try all services until one succeeds