feat(sdk): initial package bootstrap for SDK (#18861)

packages/sdk/src/tool.ts

@@ -0,0 +1,113 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { z } from 'zod';
+import { zodToJsonSchema } from 'zod-to-json-schema';
+import {
+  BaseDeclarativeTool,
+  BaseToolInvocation,
+  type ToolResult,
+  type ToolInvocation,
+  Kind,
+  type MessageBus,
+} from '@google/gemini-cli-core';
+
+export { z };
+
+export interface ToolDefinition<T extends z.ZodType> {
+  name: string;
+  description: string;
+  inputSchema: T;
+}
+
+export interface Tool<T extends z.ZodType> extends ToolDefinition<T> {
+  action: (params: z.infer<T>) => Promise<unknown>;
+}
+
+class SdkToolInvocation<T extends z.ZodType> extends BaseToolInvocation<
+  z.infer<T>,
+  ToolResult
+> {
+  constructor(
+    params: z.infer<T>,
+    messageBus: MessageBus,
+    private readonly action: (params: z.infer<T>) => Promise<unknown>,
+    toolName: string,
+  ) {
+    super(params, messageBus, toolName);
+  }
+
+  getDescription(): string {
+    return `Executing ${this._toolName}...`;
+  }
+
+  async execute(
+    _signal: AbortSignal,
+    _updateOutput?: (output: string) => void,
+  ): Promise<ToolResult> {
+    try {
+      const result = await this.action(this.params);
+      const output =
+        typeof result === 'string' ? result : JSON.stringify(result, null, 2);
+      return {
+        llmContent: output,
+        returnDisplay: output,
+      };
+    } catch (error) {
+      const errorMessage =
+        error instanceof Error ? error.message : String(error);
+      return {
+        llmContent: `Error: ${errorMessage}`,
+        returnDisplay: `Error: ${errorMessage}`,
+        error: {
+          message: errorMessage,
+        },
+      };
+    }
+  }
+}
+
+export class SdkTool<T extends z.ZodType> extends BaseDeclarativeTool<
+  z.infer<T>,
+  ToolResult
+> {
+  constructor(
+    private readonly definition: Tool<T>,
+    messageBus: MessageBus,
+  ) {
+    super(
+      definition.name,
+      definition.name,
+      definition.description,
+      Kind.Other,
+      zodToJsonSchema(definition.inputSchema),
+      messageBus,
+    );
+  }
+
+  protected createInvocation(
+    params: z.infer<T>,
+    messageBus: MessageBus,
+    toolName?: string,
+  ): ToolInvocation<z.infer<T>, ToolResult> {
+    return new SdkToolInvocation(
+      params,
+      messageBus,
+      this.definition.action,
+      toolName || this.name,
+    );
+  }
+}
+
+export function tool<T extends z.ZodType>(
+  definition: ToolDefinition<T>,
+  action: (params: z.infer<T>) => Promise<unknown>,
+): Tool<T> {
+  return {
+    ...definition,
+    action,
+  };
+}