diff --git a/hermes_cli/tools_config.py b/hermes_cli/tools_config.py
index cddc664b4..65525d27d 100644
--- a/hermes_cli/tools_config.py
+++ b/hermes_cli/tools_config.py
@@ -554,6 +554,7 @@ def _get_platform_tools(
     # MCP servers are expected to be available on all platforms by default.
     # If the platform explicitly lists one or more MCP server names, treat that
     # as an allowlist. Otherwise include every globally enabled MCP server.
+    # Special sentinel: "no_mcp" in the toolset list disables all MCP servers.
     mcp_servers = config.get("mcp_servers") or {}
     enabled_mcp_servers = {
         name
@@ -561,10 +562,15 @@ def _get_platform_tools(
         if isinstance(server_cfg, dict)
         and _parse_enabled_flag(server_cfg.get("enabled", True), default=True)
     }
-    explicit_mcp_servers = explicit_passthrough & enabled_mcp_servers
-    enabled_toolsets.update(explicit_passthrough - enabled_mcp_servers)
+    # Allow "no_mcp" sentinel to opt out of all MCP servers for this platform
+    if "no_mcp" in toolset_names:
+        explicit_mcp_servers = set()
+        enabled_toolsets.update(explicit_passthrough - enabled_mcp_servers - {"no_mcp"})
+    else:
+        explicit_mcp_servers = explicit_passthrough & enabled_mcp_servers
+        enabled_toolsets.update(explicit_passthrough - enabled_mcp_servers)
     if include_default_mcp_servers:
-        if explicit_mcp_servers:
+        if explicit_mcp_servers or "no_mcp" in toolset_names:
             enabled_toolsets.update(explicit_mcp_servers)
         else:
             enabled_toolsets.update(enabled_mcp_servers)
diff --git a/tests/hermes_cli/test_tools_config.py b/tests/hermes_cli/test_tools_config.py
index b02b3c1fc..7371c89df 100644
--- a/tests/hermes_cli/test_tools_config.py
+++ b/tests/hermes_cli/test_tools_config.py
@@ -72,6 +72,45 @@ def test_get_platform_tools_keeps_enabled_mcp_servers_with_explicit_builtin_sele
     assert "web-search-prime" in enabled
 
 
+def test_get_platform_tools_no_mcp_sentinel_excludes_all_mcp_servers():
+    """The 'no_mcp' sentinel in platform_toolsets excludes all MCP servers."""
+    config = {
+        "platform_toolsets": {"cli": ["web", "terminal", "no_mcp"]},
+        "mcp_servers": {
+            "exa": {"url": "https://mcp.exa.ai/mcp"},
+            "web-search-prime": {"url": "https://api.z.ai/api/mcp/web_search_prime/mcp"},
+        },
+    }
+
+    enabled = _get_platform_tools(config, "cli")
+
+    assert "web" in enabled
+    assert "terminal" in enabled
+    assert "exa" not in enabled
+    assert "web-search-prime" not in enabled
+    assert "no_mcp" not in enabled
+
+
+def test_get_platform_tools_no_mcp_sentinel_does_not_affect_other_platforms():
+    """The 'no_mcp' sentinel only affects the platform it's configured on."""
+    config = {
+        "platform_toolsets": {
+            "api_server": ["web", "terminal", "no_mcp"],
+        },
+        "mcp_servers": {
+            "exa": {"url": "https://mcp.exa.ai/mcp"},
+        },
+    }
+
+    # api_server should exclude MCP
+    api_enabled = _get_platform_tools(config, "api_server")
+    assert "exa" not in api_enabled
+
+    # cli (not configured with no_mcp) should include MCP
+    cli_enabled = _get_platform_tools(config, "cli")
+    assert "exa" in cli_enabled
+
+
 def test_toolset_has_keys_for_vision_accepts_codex_auth(tmp_path, monkeypatch):
     monkeypatch.setenv("HERMES_HOME", str(tmp_path))
     (tmp_path / "auth.json").write_text(