diff --git a/doc/usage.md b/doc/usage.md
index 5d075b9..96d6d2d 100644
--- a/doc/usage.md
+++ b/doc/usage.md
@@ -52,11 +52,11 @@ o tail    # stream chat output
 <table align="center" width="90%">
   <tr>
     <td width="50%" align="center">
-      <a href="img/ollie-ui-composition.png"><img src="img/ollie-ui-composition.png" alt="Ollie UI composition" width="95%"></a>
+      <a href="img/ollie-ui-composition.png"><img src="img/ollie-ui-composition.png" alt="Screenshot of o tui: two tmux panes showing chat output and prompt input, with agent state in the status bar" width="95%"></a>
       <br><em>o tui — tmux + shell commands</em>
     </td>
     <td width="50%" align="center">
-      <a href="img/ollie-acme.png"><img src="img/ollie-acme.png" alt="Ollie in acme" width="95%"></a>
+      <a href="img/ollie-acme.png"><img src="img/ollie-acme.png" alt="Screenshot of ollie running in the acme text editor: multiple windows showing session tree, chat, and prompts" width="95%"></a>
       <br><em>acme — Plan 9 editor</em>
     </td>
   </tr>
@@ -163,7 +163,7 @@ echo "list 5 blog post ideas" | o generate | head -3 | o generate
 commands in two panes, with agent state in the tmux status bar:
 
 <p align="center">
-  <a href="img/ollie-tui.png"><img src="img/ollie-tui.png" alt="Ollie TUI layout" width="75%"></a>
+  <a href="img/ollie-tui.png"><img src="img/ollie-tui.png" alt="Screenshot of the o tui tmux layout: chat pane on top, prompt REPL on bottom, agent state in status bar" width="75%"></a>
 </p>
 
 ### Usage