Add support for showing descriptions of CLI tools (#1052)

Adds support for /tools desc to show the full description of tools as provided to the model.

docs/cli/commands.md

@@ -61,6 +61,13 @@ Slash commands provide meta-level control over the CLI itself. They can typicall
 
   - **Description:** Displays a list of all the tools that are currently available to the model.
   - **Action:** Outputs a list of the available tools.
+  - **Sub-commands:**
+    - **`desc`** or **`descriptions`**:
+      - **Description:** Shows detailed descriptions of each tool.
+      - **Action:** Displays each tool's name with its full description as provided to the model.
+    - **`nodesc`** or **`nodescriptions`**:
+      - **Description:** Hides tool descriptions, showing only the tool names.
+      - **Action:** Displays a compact list with only tool names.
 
 - **`/compress`**
 

packages/cli/src/ui/hooks/slashCommandProcessor.test.ts

@@ -595,14 +595,9 @@ Add any other context about the problem here.
       });
 
       // Should only show tool1 and tool2, not the MCP tools
-      expect(mockAddItem).toHaveBeenNthCalledWith(
-        2,
-        expect.objectContaining({
-          type: MessageType.INFO,
-          text: 'Available Gemini CLI tools:\n\nTool1\nTool2',
-        }),
-        expect.any(Number),
-      );
+      const message = mockAddItem.mock.calls[1][0].text;
+      expect(message).toContain('\u001b[36mTool1\u001b[0m');
+      expect(message).toContain('\u001b[36mTool2\u001b[0m');
       expect(commandResult).toBe(true);
     });
 
@@ -626,14 +621,43 @@ Add any other context about the problem here.
         commandResult = await handleSlashCommand('/tools');
       });
 
-      expect(mockAddItem).toHaveBeenNthCalledWith(
-        2,
-        expect.objectContaining({
-          type: MessageType.INFO,
-          text: 'Available Gemini CLI tools:\n\n',
+      const message = mockAddItem.mock.calls[1][0].text;
+      expect(message).toContain('No tools available');
+      expect(commandResult).toBe(true);
+    });
+
+    it('should display tool descriptions when /tools desc is used', async () => {
+      const mockTools = [
+        {
+          name: 'tool1',
+          displayName: 'Tool1',
+          description: 'Description for Tool1',
+        },
+        {
+          name: 'tool2',
+          displayName: 'Tool2',
+          description: 'Description for Tool2',
+        },
+      ];
+
+      mockConfig = {
+        ...mockConfig,
+        getToolRegistry: vi.fn().mockResolvedValue({
+          getAllTools: vi.fn().mockReturnValue(mockTools),
         }),
-        expect.any(Number),
-      );
+      } as unknown as Config;
+
+      const { handleSlashCommand } = getProcessor();
+      let commandResult: SlashCommandActionReturn | boolean = false;
+      await act(async () => {
+        commandResult = await handleSlashCommand('/tools desc');
+      });
+
+      const message = mockAddItem.mock.calls[1][0].text;
+      expect(message).toContain('\u001b[36mTool1\u001b[0m');
+      expect(message).toContain('Description for Tool1');
+      expect(message).toContain('\u001b[36mTool2\u001b[0m');
+      expect(message).toContain('Description for Tool2');
       expect(commandResult).toBe(true);
     });
   });

packages/cli/src/ui/hooks/slashCommandProcessor.ts

@@ -419,6 +419,21 @@ export const useSlashCommandProcessor = (
         name: 'tools',
         description: 'list available Gemini CLI tools',
         action: async (_mainCommand, _subCommand, _args) => {
+          // Check if the _subCommand includes a specific flag to control description visibility
+          let useShowDescriptions = showToolDescriptions;
+          if (_subCommand === 'desc' || _subCommand === 'descriptions') {
+            useShowDescriptions = true;
+          } else if (
+            _subCommand === 'nodesc' ||
+            _subCommand === 'nodescriptions'
+          ) {
+            useShowDescriptions = false;
+          } else if (_args === 'desc' || _args === 'descriptions') {
+            useShowDescriptions = true;
+          } else if (_args === 'nodesc' || _args === 'nodescriptions') {
+            useShowDescriptions = false;
+          }
+
           const toolRegistry = await config?.getToolRegistry();
           const tools = toolRegistry?.getAllTools();
           if (!tools) {
@@ -432,11 +447,51 @@ export const useSlashCommandProcessor = (
 
           // Filter out MCP tools by checking if they have a serverName property
           const geminiTools = tools.filter((tool) => !('serverName' in tool));
-          const geminiToolList = geminiTools.map((tool) => tool.displayName);
+
+          let message = 'Available Gemini CLI tools:\n\n';
+
+          if (geminiTools.length > 0) {
+            geminiTools.forEach((tool) => {
+              if (useShowDescriptions && tool.description) {
+                // Format tool name in cyan using simple ANSI cyan color
+                message += `  - \u001b[36m${tool.displayName}\u001b[0m: `;
+
+                // Apply green color to the description text
+                const greenColor = '\u001b[32m';
+                const resetColor = '\u001b[0m';
+
+                // Handle multi-line descriptions by properly indenting and preserving formatting
+                const descLines = tool.description.split('\n');
+                message += `${greenColor}${descLines[0]}${resetColor}\n`;
+
+                // If there are multiple lines, add proper indentation for each line
+                if (descLines.length > 1) {
+                  for (let i = 1; i < descLines.length; i++) {
+                    // Skip empty lines at the end
+                    if (
+                      i === descLines.length - 1 &&
+                      descLines[i].trim() === ''
+                    )
+                      continue;
+                    message += `      ${greenColor}${descLines[i]}${resetColor}\n`;
+                  }
+                }
+              } else {
+                // Use cyan color for the tool name even when not showing descriptions
+                message += `  - \u001b[36m${tool.displayName}\u001b[0m\n`;
+              }
+            });
+          } else {
+            message += '  No tools available\n';
+          }
+          message += '\n';
+
+          // Make sure to reset any ANSI formatting at the end to prevent it from affecting the terminal
+          message += '\u001b[0m';
 
           addMessage({
             type: MessageType.INFO,
-            content: `Available Gemini CLI tools:\n\n${geminiToolList.join('\n')}`,
+            content: message,
             timestamp: new Date(),
           });
         },