fix: mark card field as optional in message tool schema

The `createMessageToolCardSchema()` helper returned a bare `Type.Object()`
which TypeBox treats as required when merged into the parent tool schema via
`Type.Object({ card: ... })`. This caused schema validation to reject
media-only sends on Feishu and MSTeams with "must have required property
card", even though the implementation correctly treats card as optional.

Wrap the return value in `Type.Optional()` so the card field is excluded
from the JSON Schema `required` array. Fixes the catch-22 where omitting
card fails validation and including an empty card triggers the runtime
"does not support card with media" guard.

Closes #53697

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

extensions/feishu/src/channel.test.ts

@@ -576,6 +576,45 @@ describe("feishuPlugin actions", () => {
     ).rejects.toThrow("Feishu thread-reply requires messageId.");
   });
 
+  it("declares card as optional in the tool schema", () => {
+    const discovery = feishuPlugin.actions?.describeMessageTool?.({ cfg });
+    const schema = Array.isArray(discovery?.schema) ? discovery.schema[0] : discovery?.schema;
+    const cardSchema = schema?.properties?.card;
+    expect(cardSchema).toBeDefined();
+    // TypeBox marks Optional schemas with Symbol(TypeBox.Optional) = "Optional".
+    expect(
+      (cardSchema as unknown as Record<symbol, unknown>)?.[Symbol.for("TypeBox.Optional")],
+    ).toBe("Optional");
+  });
+
+  it("sends media-only messages without requiring card", async () => {
+    feishuOutboundSendMediaMock.mockResolvedValueOnce({
+      channel: "feishu",
+      messageId: "om_media_only",
+      details: { messageId: "om_media_only", chatId: "oc_group_1" },
+    });
+
+    const result = await feishuPlugin.actions?.handleAction?.({
+      action: "send",
+      params: {
+        to: "chat:oc_group_1",
+        media: "https://example.com/image.png",
+      },
+      cfg,
+      accountId: undefined,
+      toolContext: {},
+      mediaLocalRoots: [],
+    } as never);
+
+    expect(feishuOutboundSendMediaMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        to: "chat:oc_group_1",
+        mediaUrl: "https://example.com/image.png",
+      }),
+    );
+    expect(result?.details).toMatchObject({ messageId: "om_media_only" });
+  });
+
   it("fails for unsupported action names", async () => {
     await expect(
       feishuPlugin.actions?.handleAction?.({

src/plugin-sdk/channel-actions.ts

@@ -25,11 +25,13 @@ export function createMessageToolButtonsSchema(): TSchema {
 
 /** Schema helper for channels that accept provider-native card payloads. */
 export function createMessageToolCardSchema(): TSchema {
-  return Type.Object(
-    {},
-    {
-      additionalProperties: true,
-      description: "Structured card payload for channels that support card-style messages.",
-    },
+  return Type.Optional(
+    Type.Object(
+      {},
+      {
+        additionalProperties: true,
+        description: "Structured card payload for channels that support card-style messages.",
+      },
+    ),
   );
 }