use json block for mcp tool output (and re-enable markdown rendering) (#635)

3 files changed, 8 insertions, 5 deletions

diff --git a/packages/server/src/tools/mcp-tool.test.ts b/packages/server/src/tools/mcp-tool.test.ts
index 331696f7..5c784c5d 100644
--- a/packages/server/src/tools/mcp-tool.test.ts
+++ b/packages/server/src/tools/mcp-tool.test.ts
@@ -116,7 +116,8 @@ describe('DiscoveredMCPTool', () => {
           timeout: MCP_TOOL_DEFAULT_TIMEOUT_MSEC,
         },
       );
-      const expectedOutput = JSON.stringify(expectedMcpResult, null, 2);
+      const expectedOutput =
+        '```json\n' + JSON.stringify(expectedMcpResult, null, 2) + '\n```';
       expect(result.llmContent).toBe(expectedOutput);
       expect(result.returnDisplay).toBe(expectedOutput);
     });
diff --git a/packages/server/src/tools/mcp-tool.ts b/packages/server/src/tools/mcp-tool.ts
index 80e6bbde..d02b8632 100644
--- a/packages/server/src/tools/mcp-tool.ts
+++ b/packages/server/src/tools/mcp-tool.ts
@@ -42,7 +42,7 @@ Returns the MCP server response as a json string.
       name,
       description,
       parameterSchema,
-      false, // isOutputMarkdown
+      true, // isOutputMarkdown
       false, // canUpdateOutput
     );
   }
@@ -93,9 +93,10 @@ Returns the MCP server response as a json string.
         timeout: this.timeout ?? MCP_TOOL_DEFAULT_TIMEOUT_MSEC,
       },
     );
+    const output = '```json\n' + JSON.stringify(result, null, 2) + '\n```';
     return {
-      llmContent: JSON.stringify(result, null, 2),
-      returnDisplay: JSON.stringify(result, null, 2),
+      llmContent: output,
+      returnDisplay: output,
     };
   }
 }
diff --git a/packages/server/src/tools/tool-registry.test.ts b/packages/server/src/tools/tool-registry.test.ts
index c93109ae..121e91c8 100644
--- a/packages/server/src/tools/tool-registry.test.ts
+++ b/packages/server/src/tools/tool-registry.test.ts
@@ -768,7 +768,8 @@ describe('DiscoveredMCPTool', () => {
         timeout: 10 * 60 * 1000,
       },
     );
-    const expectedOutput = JSON.stringify(mcpResult, null, 2);
+    const expectedOutput =
+      '```json\n' + JSON.stringify(mcpResult, null, 2) + '\n```';
     expect(result.llmContent).toBe(expectedOutput);
     expect(result.returnDisplay).toBe(expectedOutput);
   });