diff --git a/src/nodered_mcp/tools/flows.py b/src/nodered_mcp/tools/flows.py
index 1d86ead..4f864d8 100644
--- a/src/nodered_mcp/tools/flows.py
+++ b/src/nodered_mcp/tools/flows.py
@@ -75,7 +75,15 @@ async def update_flows(flows_json: str, deployment_type: str = "full") -> str:
 
     Returns:
         Confirmation message.
+
+    Raises:
+        ValueError: If deployment_type is not one of: full, nodes, flows, reload.
     """
+    _VALID_DEPLOYMENT_TYPES = ("full", "nodes", "flows", "reload")
+    if deployment_type not in _VALID_DEPLOYMENT_TYPES:
+        raise ValueError(
+            f"Invalid deployment_type '{deployment_type}'. Must be one of: {', '.join(_VALID_DEPLOYMENT_TYPES)}"
+        )
     client = get_client()
     flows = json.loads(flows_json)
     await client.update_flows(flows, deployment_type=deployment_type)
@@ -144,9 +152,15 @@ async def create_flow(flow_json: str) -> FlowCreateResult:
 
     Returns:
         FlowCreateResult with the new flow ID.
+
+    Raises:
+        ValueError: If flow_json is not valid JSON.
     """
+    try:
+        flow = json.loads(flow_json)
+    except json.JSONDecodeError as e:
+        raise ValueError(f"Invalid JSON in flow_json: {e}") from e
     client = get_client()
-    flow = json.loads(flow_json)
     result = await client.create_flow(flow)
     return FlowCreateResult.from_api(result)
 
@@ -187,7 +201,12 @@ async def set_flows_state(state: str) -> FlowState:
 
     Returns:
         FlowState with new state.
+
+    Raises:
+        ValueError: If state is not "start" or "stop".
     """
+    if state not in ("start", "stop"):
+        raise ValueError(f"Invalid state '{state}'. Must be 'start' or 'stop'.")
     client = get_client()
     raw_state = await client.set_flows_state(state)
     return FlowState.from_api(raw_state)
diff --git a/src/nodered_mcp/tools/utility.py b/src/nodered_mcp/tools/utility.py
index 509994a..9846f99 100644
--- a/src/nodered_mcp/tools/utility.py
+++ b/src/nodered_mcp/tools/utility.py
@@ -2,6 +2,32 @@
 
 from nodered_mcp.server import mcp
 
+# Centralized endpoint registry: maps path to (method, description, implemented)
+_ENDPOINT_REGISTRY = [
+    ("GET",   "/flows",                "Get all flows",                    True),
+    ("GET",   "/flows/formatted",      "Get flows with formatted summary", True),
+    ("GET",   "/flows/visualize",      "Visualize flow structure",         True),
+    ("POST",  "/flows",                "Update all flows",                 True),
+    ("GET",   "/flow/:id",             "Get a specific flow",              True),
+    ("PUT",   "/flow/:id",             "Update a specific flow",           True),
+    ("PATCH", "/flow/:id",             "Patch a flow incrementally",       True),
+    ("DELETE","/flow/:id",             "Delete a specific flow",           True),
+    ("POST",  "/flow",                 "Create a new flow",                True),
+    ("GET",   "/flows/state",          "Get the state of flows",           True),
+    ("POST",  "/flows/state",          "Set the state of flows",           True),
+    ("GET",   "/tabs",                 "List all flow tabs",               True),
+    ("GET",   "/nodes",                "Get list of installed nodes",      True),
+    ("GET",   "/nodes/:module",        "Get node module info",             True),
+    ("GET",   "/nodes/search",         "Search for nodes",                 True),
+    ("GET",   "/nodes/find",           "Find nodes by type",               True),
+    ("POST",  "/nodes/:module/toggle", "Toggle node module",               True),
+    ("POST",  "/nodes",                "Install a new node module",        False),
+    ("GET",   "/settings",             "Get runtime settings",             True),
+    ("GET",   "/diagnostics",          "Get diagnostics information",      True),
+    ("POST",  "/inject/:id",           "Trigger an inject node",           True),
+    ("GET",   "/lint/:id",             "Lint flow layout",                 True),
+]
+
 
 @mcp.tool()
 async def api_help() -> str:
@@ -9,23 +35,8 @@ async def api_help() -> str:
 
     Returns:
         Markdown table of API endpoints and their MCP implementation status.
+        Endpoints are defined in the centralized _ENDPOINT_REGISTRY.
     """
-    endpoints = [
-        ("GET", "/flows", "Get all flows", True),
-        ("POST", "/flows", "Update all flows", True),
-        ("GET", "/flow/:id", "Get a specific flow", True),
-        ("PUT", "/flow/:id", "Update a specific flow", True),
-        ("DELETE", "/flow/:id", "Delete a specific flow", True),
-        ("POST", "/flow", "Create a new flow", True),
-        ("GET", "/flows/state", "Get the state of flows", True),
-        ("POST", "/flows/state", "Set the state of flows", True),
-        ("GET", "/nodes", "Get list of installed nodes", True),
-        ("POST", "/nodes", "Install a new node module", False),
-        ("GET", "/settings", "Get runtime settings", True),
-        ("GET", "/diagnostics", "Get diagnostics information", True),
-        ("POST", "/inject/:id", "Trigger an inject node", True),
-    ]
-
     output = [
         "# Node-RED API Help",
         "",
@@ -33,8 +44,8 @@ async def api_help() -> str:
         "|--------|------|-------------|---------------------|",
     ]
 
-    for method, path, description, implemented in endpoints:
-        status = "✅" if implemented else "❌"
+    for method, path, description, implemented in _ENDPOINT_REGISTRY:
+        status = "\u2705" if implemented else "\u274c"
         output.append(f"| {method} | {path} | {description} | {status} |")
 
     return "\n".join(output)