docs: add tool visibility and restructure _meta.ui (#131)

* docs: add tool visibility and restructure _meta.ui

- Restructure tool metadata: `_meta["ui/resourceUri"]` → `_meta.ui.resourceUri`
- Add `visibility` array field: ["model"], ["apps"], or ["model", "apps"]
- Default ["model"] preserves standard MCP behavior
- ["apps"] enables widget-only tools hidden from agent
- Add McpUiToolMeta interface for type safety
- Add Design Decision #4 explaining approach vs OpenAI's two-field model

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Co-Authored-By: Claude <noreply@anthropic.com>

* address PR review comments

- Change default visibility to ["model", "apps"]
- Add deprecation notice for flat ui/resourceUri format
- Add McpUiToolMeta and McpUiToolVisibility to spec.types.ts
- Improve tools/list and tools/call behavior wording

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Co-Authored-By: Claude <noreply@anthropic.com>

* chore: regenerate schemas for McpUiToolMeta types

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Co-Authored-By: Claude <noreply@anthropic.com>

* feat: tool visibility and nested _meta.ui format

- Rename visibility "apps" → "app" in McpUiToolVisibility type
- Add _meta.ui.resourceUri nested format (deprecate flat format)
- Add getToolUiResourceUri() utility with backward compatibility
- Add visibility demo to system-monitor-server:
  - get-system-stats: visibility ["model"] with resourceUri
  - refresh-stats: visibility ["app"] (app-only polling)
- Update all example servers to use new _meta.ui format
- Add 11 unit tests for getToolUiResourceUri()

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Co-Authored-By: Claude <noreply@anthropic.com>

* chore: regenerate schemas with updated dependencies

* feat: export McpUiToolMeta type and add type annotations

- Export McpUiToolMeta and McpUiToolVisibility types from types.ts
- Export corresponding Zod schemas (McpUiToolMetaSchema, McpUiToolVisibilitySchema)
- Add `as McpUiToolMeta` type annotations to all example servers
- Update docs/quickstart.md with proper typing

Ensures type safety for `_meta.ui` tool metadata across the codebase.

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Co-Authored-By: Claude <noreply@anthropic.com>

* feat: add server helpers and optional connect() transport

Add `src/server/` with convenience functions for registering MCP App tools
and resources:

- `registerAppTool(server, name, config, handler)`
- `registerAppResource(server, name, uri, config, callback)`

The `transport` parameter in `App.connect()` is now optional, defaulting to
`PostMessageTransport(window.parent)`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Update src/server/index.ts

Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>

* feat: update McpUiAppToolConfig to support both _meta.ui and flat formats

* refactor: simplify server helper imports

* docs: add deprecation notice and improve resourceUri documentation

* feat: add backward compat normalization in registerAppTool

- If _meta.ui.resourceUri is set, also set legacy flat key
- If legacy flat key is set, also set _meta.ui.resourceUri
- Preserves existing visibility when merging
- Does not overwrite if both formats already set

* refactor: avoid mutating config arg in registerAppTool

* style: format with prettier

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Olivier Chafik <ochafik@anthropic.com>
Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>

src/generated/schema.json

@@ -3796,6 +3796,34 @@
       "required": ["method", "params"],
       "additionalProperties": false
     },
+    "McpUiToolMeta": {
+      "$schema": "https://json-schema.org/draft/2020-12/schema",
+      "type": "object",
+      "properties": {
+        "resourceUri": {
+          "type": "string"
+        },
+        "visibility": {
+          "description": "Who can access this tool. Default: [\"model\", \"app\"]\n- \"model\": Tool visible to and callable by the agent\n- \"app\": Tool callable by the app from this server only",
+          "type": "array",
+          "items": {
+            "description": "Tool visibility scope - who can access the tool.",
+            "anyOf": [
+              {
+                "type": "string",
+                "const": "model"
+              },
+              {
+                "type": "string",
+                "const": "app"
+              }
+            ]
+          }
+        }
+      },
+      "required": ["resourceUri"],
+      "additionalProperties": false
+    },
     "McpUiToolResultNotification": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
       "type": "object",
@@ -4154,6 +4182,20 @@
       },
       "required": ["method", "params"],
       "additionalProperties": false
+    },
+    "McpUiToolVisibility": {
+      "$schema": "https://json-schema.org/draft/2020-12/schema",
+      "description": "Tool visibility scope - who can access the tool.",
+      "anyOf": [
+        {
+          "type": "string",
+          "const": "model"
+        },
+        {
+          "type": "string",
+          "const": "app"
+        }
+      ]
     }
   }
 }

src/generated/schema.test.ts

@@ -103,6 +103,14 @@ export type McpUiRequestDisplayModeResultSchemaInferredType = z.infer<
   typeof generated.McpUiRequestDisplayModeResultSchema
 >;
 
+export type McpUiToolVisibilitySchemaInferredType = z.infer<
+  typeof generated.McpUiToolVisibilitySchema
+>;
+
+export type McpUiToolMetaSchemaInferredType = z.infer<
+  typeof generated.McpUiToolMetaSchema
+>;
+
 export type McpUiMessageRequestSchemaInferredType = z.infer<
   typeof generated.McpUiMessageRequestSchema
 >;
@@ -237,6 +245,14 @@ expectType<spec.McpUiRequestDisplayModeResult>(
 expectType<McpUiRequestDisplayModeResultSchemaInferredType>(
   {} as spec.McpUiRequestDisplayModeResult,
 );
+expectType<spec.McpUiToolVisibility>(
+  {} as McpUiToolVisibilitySchemaInferredType,
+);
+expectType<McpUiToolVisibilitySchemaInferredType>(
+  {} as spec.McpUiToolVisibility,
+);
+expectType<spec.McpUiToolMeta>({} as McpUiToolMetaSchemaInferredType);
+expectType<McpUiToolMetaSchemaInferredType>({} as spec.McpUiToolMeta);
 expectType<spec.McpUiMessageRequest>(
   {} as McpUiMessageRequestSchemaInferredType,
 );

src/generated/schema.ts

@@ -449,6 +449,37 @@ export const McpUiRequestDisplayModeResultSchema = z.looseObject({
   ),
 });
 
+/**
+ * @description Tool visibility scope - who can access the tool.
+ */
+export const McpUiToolVisibilitySchema = z
+  .union([z.literal("model"), z.literal("app")])
+  .describe("Tool visibility scope - who can access the tool.");
+
+/**
+ * @description UI-related metadata for tools.
+ */
+export const McpUiToolMetaSchema = z.object({
+  /**
+   * URI of the UI resource to display for this tool.
+   * This is converted to `_meta["ui/resourceUri"]`.
+   *
+   * @example "ui://weather/widget.html"
+   */
+  resourceUri: z.string(),
+  /**
+   * @description Who can access this tool. Default: ["model", "app"]
+   * - "model": Tool visible to and callable by the agent
+   * - "app": Tool callable by the app from this server only
+   */
+  visibility: z
+    .array(McpUiToolVisibilitySchema)
+    .optional()
+    .describe(
+      'Who can access this tool. Default: ["model", "app"]\n- "model": Tool visible to and callable by the agent\n- "app": Tool callable by the app from this server only',
+    ),
+});
+
 /**
  * @description Request to send a message to the host's chat interface.
  * @see {@link app.App.sendMessage} for the method that sends this request