Release v1.6.0 (#324)

* Update version and changelog for v1.6.0
* Update docs
diff --git a/docs/dyn/content_v2.accounts.html b/docs/dyn/content_v2.accounts.html
index ea13e2f..0a01c5f 100644
--- a/docs/dyn/content_v2.accounts.html
+++ b/docs/dyn/content_v2.accounts.html
@@ -82,25 +82,25 @@
 <p class="firstline">Retrieves, inserts, updates, and deletes multiple Merchant Center (sub-)accounts in a single request.</p>
 <p class="toc_element">
   <code><a href="#delete">delete(merchantId, accountId, dryRun=None)</a></code></p>
-<p class="firstline">Deletes a Merchant Center sub-account.</p>
+<p class="firstline">Deletes a Merchant Center sub-account. This method can only be called for multi-client accounts.</p>
 <p class="toc_element">
   <code><a href="#get">get(merchantId, accountId)</a></code></p>
-<p class="firstline">Retrieves a Merchant Center account.</p>
+<p class="firstline">Retrieves a Merchant Center account. This method can only be called for accounts to which the managing account has access: either the managing account itself or sub-accounts if the managing account is a multi-client account.</p>
 <p class="toc_element">
   <code><a href="#insert">insert(merchantId, body, dryRun=None)</a></code></p>
-<p class="firstline">Creates a Merchant Center sub-account.</p>
+<p class="firstline">Creates a Merchant Center sub-account. This method can only be called for multi-client accounts.</p>
 <p class="toc_element">
   <code><a href="#list">list(merchantId, pageToken=None, maxResults=None)</a></code></p>
-<p class="firstline">Lists the sub-accounts in your Merchant Center account.</p>
+<p class="firstline">Lists the sub-accounts in your Merchant Center account. This method can only be called for multi-client accounts.</p>
 <p class="toc_element">
   <code><a href="#list_next">list_next(previous_request, previous_response)</a></code></p>
 <p class="firstline">Retrieves the next page of results.</p>
 <p class="toc_element">
   <code><a href="#patch">patch(merchantId, accountId, body, dryRun=None)</a></code></p>
-<p class="firstline">Updates a Merchant Center account. This method supports patch semantics.</p>
+<p class="firstline">Updates a Merchant Center account. This method can only be called for multi-client accounts. This method supports patch semantics.</p>
 <p class="toc_element">
   <code><a href="#update">update(merchantId, accountId, body, dryRun=None)</a></code></p>
-<p class="firstline">Updates a Merchant Center account.</p>
+<p class="firstline">Updates a Merchant Center account. This method can only be called for multi-client accounts.</p>
 <h3>Method Details</h3>
 <div class="method">
     <code class="details" id="authinfo">authinfo()</code>
@@ -215,7 +215,7 @@
 
 <div class="method">
     <code class="details" id="delete">delete(merchantId, accountId, dryRun=None)</code>
-  <pre>Deletes a Merchant Center sub-account.
+  <pre>Deletes a Merchant Center sub-account. This method can only be called for multi-client accounts.
 
 Args:
   merchantId: string, The ID of the managing account. (required)
@@ -226,7 +226,7 @@
 
 <div class="method">
     <code class="details" id="get">get(merchantId, accountId)</code>
-  <pre>Retrieves a Merchant Center account.
+  <pre>Retrieves a Merchant Center account. This method can only be called for accounts to which the managing account has access: either the managing account itself or sub-accounts if the managing account is a multi-client account.
 
 Args:
   merchantId: string, The ID of the managing account. (required)
@@ -260,7 +260,7 @@
 
 <div class="method">
     <code class="details" id="insert">insert(merchantId, body, dryRun=None)</code>
-  <pre>Creates a Merchant Center sub-account.
+  <pre>Creates a Merchant Center sub-account. This method can only be called for multi-client accounts.
 
 Args:
   merchantId: string, The ID of the managing account. (required)
@@ -319,7 +319,7 @@
 
 <div class="method">
     <code class="details" id="list">list(merchantId, pageToken=None, maxResults=None)</code>
-  <pre>Lists the sub-accounts in your Merchant Center account.
+  <pre>Lists the sub-accounts in your Merchant Center account. This method can only be called for multi-client accounts.
 
 Args:
   merchantId: string, The ID of the managing account. (required)
@@ -374,7 +374,7 @@
 
 <div class="method">
     <code class="details" id="patch">patch(merchantId, accountId, body, dryRun=None)</code>
-  <pre>Updates a Merchant Center account. This method supports patch semantics.
+  <pre>Updates a Merchant Center account. This method can only be called for multi-client accounts. This method supports patch semantics.
 
 Args:
   merchantId: string, The ID of the managing account. (required)
@@ -434,7 +434,7 @@
 
 <div class="method">
     <code class="details" id="update">update(merchantId, accountId, body, dryRun=None)</code>
-  <pre>Updates a Merchant Center account.
+  <pre>Updates a Merchant Center account. This method can only be called for multi-client accounts.
 
 Args:
   merchantId: string, The ID of the managing account. (required)