diff --git a/src/lib/agent/runner/harness/pi/orchestrator-tools.ts b/src/lib/agent/runner/harness/pi/orchestrator-tools.ts
index 42aa778c..83ebbadc 100644
--- a/src/lib/agent/runner/harness/pi/orchestrator-tools.ts
+++ b/src/lib/agent/runner/harness/pi/orchestrator-tools.ts
@@ -18,6 +18,7 @@ import {
   applyComplete,
   applyEnqueue,
   applyReadHandoffs,
+  COMPLETE_TASK_DESCRIPTION,
   ENQUEUE_MODEL_DESCRIPTION,
   HANDOFF_FIELDS,
   NOT_NEEDED_REASON_ASK,
@@ -138,10 +139,9 @@ export function createPiOrchestratorTools(
   const completeTask = defineTool({
     name: 'complete_task',
     label: 'Complete task',
-    description:
-      "Report the outcome of your task. Always call this exactly once when you finish, with a structured handoff for the next agent. Use status 'not needed' when the task does not apply to this project and you cannot do it (say why in the handoff) — not 'done'.",
+    description: COMPLETE_TASK_DESCRIPTION,
     promptSnippet:
-      'complete_task(status, handoff) — report your outcome exactly once when done',
+      'complete_task(status, handoff) — report your outcome exactly once when done, with goals/did/forNextAgent nested inside handoff',
     parameters: COMPLETE_PARAMS,
     execute(_id, args) {
       const res = applyComplete(ctx, args as CompleteArgs);
diff --git a/src/lib/agent/runner/sequence/orchestrator/__tests__/handoff-schema-parity.test.ts b/src/lib/agent/runner/sequence/orchestrator/__tests__/handoff-schema-parity.test.ts
index e4546b51..62b14780 100644
--- a/src/lib/agent/runner/sequence/orchestrator/__tests__/handoff-schema-parity.test.ts
+++ b/src/lib/agent/runner/sequence/orchestrator/__tests__/handoff-schema-parity.test.ts
@@ -5,8 +5,16 @@
  * asked for a report section it could not submit.
  */
 import { describe, it, expect } from 'vitest';
-import { HANDOFF_FIELDS, HANDOFF_SHAPE_KEYS } from '../queue-tools';
-import { PI_HANDOFF_PARAM_KEYS } from '../../../harness/pi/orchestrator-tools';
+import {
+  COMPLETE_TASK_DESCRIPTION,
+  HANDOFF_FIELDS,
+  HANDOFF_SHAPE_KEYS,
+  type OrchestratorToolsContext,
+} from '../queue-tools';
+import {
+  createPiOrchestratorTools,
+  PI_HANDOFF_PARAM_KEYS,
+} from '../../../harness/pi/orchestrator-tools';
 
 describe('complete_task handoff schema', () => {
   it('exposes the same fields on both harnesses', () => {
@@ -33,3 +41,29 @@ describe('complete_task handoff schema', () => {
     },
   );
 });
+
+describe('complete_task description', () => {
+  const piCompleteTask = () => {
+    const ctx = { validTypes: [] } as unknown as OrchestratorToolsContext;
+    const tool = createPiOrchestratorTools(ctx).find(
+      (t) => (t as unknown as { name: string }).name === 'complete_task',
+    );
+    return tool as unknown as { description: string };
+  };
+
+  it('shares one tool description with the MCP server', () => {
+    expect(piCompleteTask().description).toBe(COMPLETE_TASK_DESCRIPTION);
+  });
+
+  // An agent that cannot see the nesting spends a turn on a rejected flat call.
+  it.each(['goals', 'did', 'forNextAgent'])(
+    'names %s as a field that goes inside the nested handoff',
+    (field) => {
+      expect(COMPLETE_TASK_DESCRIPTION).toContain(field);
+    },
+  );
+
+  it('says the handoff is nested', () => {
+    expect(COMPLETE_TASK_DESCRIPTION).toMatch(/nested object/);
+  });
+});
diff --git a/src/lib/agent/runner/sequence/orchestrator/queue-tools.ts b/src/lib/agent/runner/sequence/orchestrator/queue-tools.ts
index 5f1fa344..2e295582 100644
--- a/src/lib/agent/runner/sequence/orchestrator/queue-tools.ts
+++ b/src/lib/agent/runner/sequence/orchestrator/queue-tools.ts
@@ -48,6 +48,22 @@ export const ENQUEUE_MODEL_DESCRIPTION = `Optional model override for this task.
   ...VALID_MODELS,
 ].join(', ')}.`;
 
+/**
+ * The `complete_task` tool description, shared by both harnesses' schemas so
+ * the outcome contract cannot drift — the same discipline {@link HANDOFF_FIELDS}
+ * applies to the fields inside the handoff.
+ *
+ * The closing sentence names the nesting because agents kept learning it from a
+ * rejection instead: a first call with `goals`/`did`/`forNextAgent` at the top
+ * level fails schema validation, and reading that error back was the only place
+ * the shape was stated. Naming it where the agent fills the call in costs
+ * nothing, the same reasoning as {@link ENQUEUE_MODEL_DESCRIPTION}.
+ */
+export const COMPLETE_TASK_DESCRIPTION =
+  'Report the outcome of your task. Always call this exactly once when you finish, with a structured handoff for the next agent. ' +
+  "Use status 'not needed' when the task does not apply to this project and you cannot do it (say why in the handoff) — not 'done'. " +
+  'The handoff is one nested object: put `goals`, `did` and `forNextAgent` — all three required — inside `handoff`, along with any optional fields, never at the top level.';
+
 /** The per-task remark ask, shared by both harnesses' complete_task schemas. */
 export const REMARK_ASK =
   'What information or guidance would have been useful to have in the integration prompt or documentation for this task — specifically anything that would have prevented tool failures, erroneous edits, or other wasted turns.';
@@ -512,7 +528,7 @@ export function buildOrchestratorTools(
 
   const completeTask = tool(
     'complete_task',
-    "Report the outcome of your task. Always call this exactly once when you finish, with a structured handoff for the next agent. Use status 'not needed' when the task does not apply to this project and you cannot do it (say why in the handoff) — not 'done'.",
+    COMPLETE_TASK_DESCRIPTION,
     COMPLETE_SHAPE,
     ((args: CompleteArgs) => {
       const res = applyComplete(ctx, args);