1 files changed, 41 insertions, 0 deletions
diff --git a/packages/core/src/tools/retrieve.ts b/packages/core/src/tools/retrieve.ts
new file mode 100644
index 0000000..93f4c89
--- /dev/null
+++ b/packages/core/src/tools/retrieve.ts
@@ -0,0 +1,41 @@
+import { z } from "zod";
+import type { ToolDefinition } from "../types/index.js";
+
+export interface RetrieveCallbacks {
+	getResult(
+		agentId: string,
+	): Promise<{ status: "done"; result: string } | { status: "error"; error: string }>;
+}
+
+export function createRetrieveTool(callbacks: RetrieveCallbacks): ToolDefinition {
+	return {
+		name: "retrieve",
+		description: [
+			"Wait for a child agent to finish and retrieve its result. This tool BLOCKS until the child completes.",
+			"",
+			"Pass the agent_id returned by the summon tool. Once the child finishes, its final output is returned.",
+			"If the child encountered an error, the error message is returned instead.",
+			"",
+			"Typical usage:",
+			'  1. summon({ task: "...", tools: [...] })  -> get agent_id',
+			"  2. ... do other work or summon more agents ...",
+			'  3. retrieve({ agent_id: "..." })  -> blocks until done, returns result',
+		].join("\n"),
+		parameters: z.object({
+			agent_id: z.string().describe("The agent_id returned by a previous summon call."),
+		}),
+		execute: async (args: Record<string, unknown>): Promise<string> => {
+			const agentId = args.agent_id as string;
+
+			try {
+				const outcome = await callbacks.getResult(agentId);
+				if (outcome.status === "done") {
+					return ["<agent_result>", outcome.result, "</agent_result>"].join("\n");
+				}
+				return `Agent error: ${outcome.error}`;
+			} catch (err) {
+				return `Error retrieving result: ${err instanceof Error ? err.message : String(err)}`;
+			}
+		},
+	};
+}