diff --git a/src/lib/smartsheet.ts b/src/lib/smartsheet.ts
index 37d1f2a..9cacc05 100644
--- a/src/lib/smartsheet.ts
+++ b/src/lib/smartsheet.ts
@@ -207,16 +207,18 @@ export async function getSheetMeta(
   if (!token) throw new Error("token is required");
 
   type ApiResponse = {
-    result: {
+    // NOTE: GET /2.0/sheets/{id} returns a FLAT response (id, name,
+    // columns at the top level), NOT wrapped in a `result` envelope.
+    // This is different from POST endpoints (which use { result: [...] }).
+    // See https://smartsheet.redoc.ly/#operation/getSheet
+    id: number;
+    name: string;
+    columns: Array<{
       id: number;
-      name: string;
-      columns: Array<{
-        id: number;
-        title: string;
-        type: string;
-        index: number;
-      }>;
-    };
+      title: string;
+      type: string;
+      index: number;
+    }>;
   };
 
   const data = await request<ApiResponse>(
@@ -225,27 +227,26 @@ export async function getSheetMeta(
     token,
   );
 
-  // Defensive: Smartsheet occasionally returns a 2xx with a body that
-  // lacks the `result` envelope (e.g. when a non-numeric / share-slug
-  // sheet ID is passed — the API doesn't reject it cleanly). Without
-  // this guard we'd crash with "Cannot read properties of undefined
-  // (reading 'id')" deep in the column-mapping render. `extractSheetId`
-  // catches the common share-slug case up front; this guard is the
-  // belt-and-suspenders for anything else.
-  if (!data?.result || data.result.id == null) {
+  // Defensive: if Smartsheet returns a 2xx without `id`, something is
+  // wrong (older API version, account-level issue, etc.). Without this
+  // guard we'd crash with "Cannot read properties of undefined (reading
+  // 'id')" deep in the column-mapping render. `extractSheetId` catches
+  // share-link slugs up front; this guard is belt-and-suspenders for
+  // anything else.
+  if (!data || data.id == null) {
     throw new SmartsheetApiError(
       502,
       `Smartsheet returned an unexpected response for sheet ${sheetId} ` +
-        `(missing result.id). If you pasted a Smartsheet share-link URL, ` +
-        `paste the numeric sheet ID instead — open the sheet in Smartsheet ` +
-        `while signed in and copy the number from the address bar.`,
+        `(missing id at top level). If you pasted a Smartsheet share-link ` +
+        `URL, paste the numeric sheet ID instead — open the sheet in ` +
+        `Smartsheet while signed in and copy the number from the address bar.`,
     );
   }
 
   return {
-    id: String(data.result.id),
-    name: data.result.name ?? "(unnamed sheet)",
-    columns: (data.result.columns ?? []).map((c) => ({
+    id: String(data.id),
+    name: data.name ?? "(unnamed sheet)",
+    columns: (data.columns ?? []).map((c) => ({
       id: c.id != null ? String(c.id) : "",
       title: c.title ?? "",
       type: c.type ?? "TEXT_NUMBER",
@@ -278,8 +279,14 @@ export async function addRow(
     return v;
   };
 
+  // NOTE: POST /2.0/sheets/{id}/rows wraps the created row(s) in
+  // `{ result: [{id, rowNumber}, ...] }` — different shape from the
+  // flat GET /2.0/sheets/{id} response. See
+  // https://smartsheet.redoc.ly/#operation/addRows
   type ApiResponse = {
-    result: { id: number; rowNumber: number };
+    result: Array<{ id: number; rowNumber: number }>;
+    resultCode?: number;
+    message?: string;
   };
 
   const data = await request<ApiResponse>(
@@ -298,9 +305,17 @@ export async function addRow(
     },
   );
 
+  const row = data?.result?.[0];
+  if (!row || row.id == null) {
+    throw new SmartsheetApiError(
+      502,
+      `Smartsheet POST /sheets/${sheetId}/rows returned no row. ` +
+        `Response: ${JSON.stringify(data).slice(0, 200)}`,
+    );
+  }
   return {
-    rowId: String(data.result.id),
-    rowNumber: data.result.rowNumber,
+    rowId: String(row.id),
+    rowNumber: row.rowNumber,
   };
 }