feat: Add expand-node tool to wiki-explorer and update tool descriptions

Wiki Explorer:
- Add expand-node tool - the critical missing tool for graph exploration
- Claude can now programmatically expand nodes to discover linked articles

Server descriptions updated to mention widget tools:
- map-server: navigate-to, get-current-view
- pdf-server: go-to-page, get-page-text, search-text, set-zoom, get-document-info
- budget-allocator: get-allocations, set-allocation, set-total-budget, etc.
- shadertoy: set-shader-source, get-shader-info
- wiki-explorer: expand-node, search-article, highlight-node, etc.

All descriptions now mention 'Use list_widget_tools to discover available actions.'

Author: ochafik

examples/budget-allocator-server/server.ts

@@ -269,7 +269,7 @@ export function createServer(): McpServer {
     {
       title: "Get Budget Data",
       description:
-        "Returns budget configuration with 24 months of historical allocations and industry benchmarks by company stage",
+        "Returns budget configuration with 24 months of historical allocations and industry benchmarks by company stage. The widget exposes tools: get-allocations (current allocations), set-allocation (adjust a category), set-total-budget (change budget), set-company-stage (change benchmark stage), get-benchmark-comparison (compare to industry). Use list_widget_tools to discover available actions.",
       inputSchema: {},
       outputSchema: BudgetDataResponseSchema,
       _meta: { ui: { resourceUri } },

examples/map-server/server.ts

@@ -148,7 +148,7 @@ export function createServer(): McpServer {
     {
       title: "Show Map",
       description:
-        "Display an interactive world map zoomed to a specific bounding box. Use the GeoCode tool to find the bounding box of a location.",
+        "Display an interactive world map zoomed to a specific bounding box. Use the GeoCode tool to find the bounding box of a location. The widget exposes tools: navigate-to (fly to a new location), get-current-view (get camera position and visible bounds). Use list_widget_tools to discover available actions.",
       inputSchema: {
         west: z
           .number()

examples/pdf-server/server.ts

@@ -136,7 +136,9 @@ Use this tool when the user asks to view, display, read, or open a PDF. Accepts:
 - URLs from list_pdfs (preloaded PDFs)
 - Any arxiv.org URL (loaded dynamically)
 
-The viewer supports zoom, navigation, text selection, and fullscreen mode.`,
+The viewer supports zoom, navigation, text selection, and fullscreen mode.
+
+The widget exposes tools: go-to-page (navigate to a page), get-page-text (extract text), search-text (find text in document), set-zoom (adjust zoom level), get-document-info (get metadata). Use list_widget_tools to discover available actions.`,
       inputSchema: {
         url: z
           .string()

examples/shadertoy-server/server.ts

@@ -49,7 +49,9 @@ LIMITATIONS - Do NOT use:
 - VR features (mainVR not available)
 
 For procedural noise:
-  float hash(vec2 p) { return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453); }`;
+  float hash(vec2 p) { return fract(sin(dot(p,vec2(127.1,311.7)))*43758.5453); }
+
+The widget exposes tools: set-shader-source (update shader code), get-shader-info (get source and errors). Compilation errors are also sent to model context. Use list_widget_tools to discover available actions.`;
 
 const DEFAULT_FRAGMENT_SHADER = `void mainImage(out vec4 fragColor, in vec2 fragCoord) {
     vec2 uv = fragCoord / iResolution.xy;

examples/wiki-explorer-server/server.ts

@@ -86,7 +86,7 @@ export function createServer(): McpServer {
     {
       title: "Get First-Degree Links",
       description:
-        "Returns all Wikipedia pages that the given page links to directly.",
+        "Returns all Wikipedia pages that the given page links to directly. The widget exposes tools: expand-node (explore a node's links - the key interaction!), search-article (find articles), get-current-article (get displayed article), highlight-node (highlight a graph node), get-visible-nodes (list visible nodes). Use list_widget_tools to discover available actions.",
       inputSchema: z.object({
         url: z
           .string()

examples/wiki-explorer-server/src/mcp-app.ts

@@ -576,6 +576,123 @@ app.registerTool(
   },
 );
 
+// Tool: Expand a node to show its linked pages
+app.registerTool(
+  "expand-node",
+  {
+    title: "Expand Node",
+    description:
+      "Expand a node to fetch and display all Wikipedia pages it links to. This is the core way to explore the graph.",
+    inputSchema: z.object({
+      identifier: z
+        .string()
+        .describe("The title or URL of the node to expand"),
+    }),
+  },
+  async (args) => {
+    const { identifier } = args as { identifier: string };
+    const lowerIdentifier = identifier.toLowerCase();
+
+    // Find node by title (case-insensitive partial match) or exact URL
+    const node = graphData.nodes.find(
+      (n) =>
+        n.url === identifier || n.title.toLowerCase().includes(lowerIdentifier),
+    );
+
+    if (!node) {
+      return {
+        content: [
+          { type: "text" as const, text: `Node not found: ${identifier}` },
+        ],
+        structuredContent: {
+          success: false,
+          error: "Node not found in graph",
+          availableNodes: graphData.nodes.map((n) => n.title),
+        },
+      };
+    }
+
+    if (node.state === "expanded") {
+      return {
+        content: [
+          {
+            type: "text" as const,
+            text: `Node "${node.title}" is already expanded`,
+          },
+        ],
+        structuredContent: {
+          success: true,
+          alreadyExpanded: true,
+          node: { url: node.url, title: node.title },
+        },
+      };
+    }
+
+    if (node.state === "error") {
+      return {
+        content: [
+          {
+            type: "text" as const,
+            text: `Node "${node.title}" has an error: ${node.errorMessage}`,
+          },
+        ],
+        structuredContent: {
+          success: false,
+          error: node.errorMessage,
+        },
+      };
+    }
+
+    try {
+      // Fetch the linked pages using the server tool
+      const result = await app.callServerTool({
+        name: "get-first-degree-links",
+        arguments: { url: node.url },
+      });
+
+      graph.warmupTicks(0);
+      handleToolResultData(result);
+
+      const response = result.structuredContent as unknown as ToolResponse;
+      const linksAdded = response?.links?.length ?? 0;
+
+      // Center on the expanded node
+      if (node.x !== undefined && node.y !== undefined) {
+        graph.centerAt(node.x, node.y, 500);
+      }
+
+      return {
+        content: [
+          {
+            type: "text" as const,
+            text: `Expanded "${node.title}" - found ${linksAdded} linked articles`,
+          },
+        ],
+        structuredContent: {
+          success: true,
+          node: { url: node.url, title: node.title },
+          linksAdded,
+        },
+      };
+    } catch (e) {
+      setNodeState(node.url, "error", "Request failed");
+      updateGraph();
+      return {
+        content: [
+          {
+            type: "text" as const,
+            text: `Failed to expand "${node.title}": ${e instanceof Error ? e.message : String(e)}`,
+          },
+        ],
+        structuredContent: {
+          success: false,
+          error: String(e),
+        },
+      };
+    }
+  },
+);
+
 // Tool: Get list of currently visible nodes in the graph
 app.registerTool(
   "get-visible-nodes",