fix: normalize MCP tool error formatting

AGENT_HANDOFF.md

@@ -105,9 +105,20 @@ Four additional MCP tools registered on the server (`src/server.js`):
 - All handlers use existing modules only (no new imports or files).
 - SDK quirk: `isError: true` wraps results in JSON-RPC error envelope (`code: -32603`).
 
+### Task 5.4 - Normalize MCP tool error formatting ✅
+
+MCP tool error formatting normalized in `src/server.js`. All 5 tool registrations now produce a single "Error:" prefix — no more duplicate `"Error: Error:"` strings.
+
+**Changes:** Each tool callback normalizes the error text before returning:
+- If `result.error` already starts with `"Error:"`, it is used as-is.
+- Otherwise, `"Error: "` is prepended.
+- `result.ok` responses are unchanged.
+
+Smoke tests: npm test 523 passed ✅ · tools/list 5 tools ✅ · ask_chatgpt single prefix ✅ · review_plan single prefix ✅
+
 ## Next Pending
 
-### Task 5.4 - Normalize MCP tool error formatting
+### Task 5.5 - Claude Code MCP configuration and local end-to-end setup
 
 ## General Rules
 

PROJECT_STATE.md

@@ -7,7 +7,7 @@ ChatGPT MCP Server
 ## Status
 
 Planning complete.
-Phase 0 complete. Phase 1 complete. Phase 2 complete. Phase 3 complete. Task 4.1 complete. Task 4.2 complete. Task 4.3 complete. Task 4.4 complete. Task 4.5 complete. Phase 4 complete. Task 5.1 complete. Task 5.2 complete. Task 5.3 complete.
+Phase 0 complete. Phase 1 complete. Phase 2 complete. Phase 3 complete. Task 4.1 complete. Task 4.2 complete. Task 4.3 complete. Task 4.4 complete. Task 4.5 complete. Phase 4 complete. Task 5.1 complete. Task 5.2 complete. Task 5.3 complete. Task 5.4 complete.
 
 ## Current Phase
 
@@ -71,7 +71,9 @@ Phase 5 - MCP Server and Tool Registration
   - missing OPENAI_API_KEY → structured tool errors (`"Error: Configuration error: OPENAI_API_KEY is missing."`) ✅
   - npm test → 523 tests pass across 18 test files, no regressions ✅
 
-- Task 5.4 — Normalize MCP tool error formatting (NEXT)
+- Task 5.4 — Normalize MCP tool error formatting ✅
+
+MCP tool error formatting normalized in `src/server.js`. All 5 tools now produce a single "Error:" prefix with no duplicates.
 
 ## Phase 3 Completion Summary
 
@@ -124,4 +126,4 @@ All five tool handlers are implemented and tested:
 
 ## Next Pending
 
-### Task 5.4 - Normalize MCP tool error formatting
+### Task 5.5 - Claude Code MCP configuration and local end-to-end setup

TASKS.md

@@ -526,4 +526,43 @@ Register `review_plan`, `review_code`, `debug_issue`, and `architecture_review`
 
 Status: ✅ Complete
 
-### Task 5.4 - Normalize MCP tool error formatting (NEXT)
+### Task 5.4 - Normalize MCP tool error formatting ✅
+
+Ensure all MCP tool error messages have a single, consistent "Error:" prefix.
+
+Before this change, handlers returned errors prefixed with `"Error: "` and server.js prepended another `"Error: "`, producing duplicates like:
+
+```
+Error: Error: Configuration error: OPENAI_API_KEY is missing.
+```
+
+**Changes made (`src/server.js`):**
+
+Each of the 5 tool registration callbacks now normalizes error text:
+
+```js
+const text = result.ok
+  ? result.answer
+  : String(result.error || "Unknown error").startsWith("Error:")
+    ? result.error
+    : `Error: ${result.error}`;
+```
+
+After fix:
+
+- `"Error: Configuration error: OPENAI_API_KEY is missing."` — single prefix ✅
+- Non-"Error:"-prefixed errors receive one prefix added by the server ✅
+- Success responses unchanged ✅
+
+Smoke tests:
+
+| Test | Result |
+|------|--------|
+| npm test | ✅ 523 passed, no regressions |
+| tools/list | ✅ 5 tools, unchanged |
+| ask_chatgpt (no API key) | ✅ Single "Error:" prefix |
+| review_plan (no API key) | ✅ Single "Error:" prefix |
+
+Status: ✅ Complete
+
+### Task 5.5 - Claude Code MCP configuration and local end-to-end setup (NEXT)

src/server.js

@@ -29,10 +29,14 @@ server.registerTool(
       sendOpenAIResponse,
     });
 
+    const text = result.ok
+      ? result.answer
+      : String(result.error || "Unknown error").startsWith("Error:")
+        ? result.error
+        : `Error: ${result.error}`;
+
     return {
-      content: [
-        { type: "text", text: result.ok ? result.answer : `Error: ${result.error}` },
-      ],
+      content: [{ type: "text", text }],
       isError: !result.ok,
       warnings: result.warnings?.length ? result.warnings : undefined,
     };
@@ -53,10 +57,14 @@ server.registerTool(
       sendOpenAIResponse,
     });
 
+    const text = result.ok
+      ? result.answer
+      : String(result.error || "Unknown error").startsWith("Error:")
+        ? result.error
+        : `Error: ${result.error}`;
+
     return {
-      content: [
-        { type: "text", text: result.ok ? result.answer : `Error: ${result.error}` },
-      ],
+      content: [{ type: "text", text }],
       isError: !result.ok,
       warnings: result.warnings?.length ? result.warnings : undefined,
     };
@@ -77,10 +85,14 @@ server.registerTool(
       sendOpenAIResponse,
     });
 
+    const text = result.ok
+      ? result.answer
+      : String(result.error || "Unknown error").startsWith("Error:")
+        ? result.error
+        : `Error: ${result.error}`;
+
     return {
-      content: [
-        { type: "text", text: result.ok ? result.answer : `Error: ${result.error}` },
-      ],
+      content: [{ type: "text", text }],
       isError: !result.ok,
       warnings: result.warnings?.length ? result.warnings : undefined,
     };
@@ -101,10 +113,14 @@ server.registerTool(
       sendOpenAIResponse,
     });
 
+    const text = result.ok
+      ? result.answer
+      : String(result.error || "Unknown error").startsWith("Error:")
+        ? result.error
+        : `Error: ${result.error}`;
+
     return {
-      content: [
-        { type: "text", text: result.ok ? result.answer : `Error: ${result.error}` },
-      ],
+      content: [{ type: "text", text }],
       isError: !result.ok,
       warnings: result.warnings?.length ? result.warnings : undefined,
     };
@@ -125,10 +141,14 @@ server.registerTool(
       sendOpenAIResponse,
     });
 
+    const text = result.ok
+      ? result.answer
+      : String(result.error || "Unknown error").startsWith("Error:")
+        ? result.error
+        : `Error: ${result.error}`;
+
     return {
-      content: [
-        { type: "text", text: result.ok ? result.answer : `Error: ${result.error}` },
-      ],
+      content: [{ type: "text", text }],
       isError: !result.ok,
       warnings: result.warnings?.length ? result.warnings : undefined,
     };