fix(fetch): add python-only readability fallback

src/fetch/README.md

@@ -33,7 +33,7 @@ The fetch tool will truncate the response, but by using the `start_index` argume
 
 ## Installation
 
-Optionally: Install node.js, this will cause the fetch server to use a different HTML simplifier that is more robust.
+Optionally: Install node.js, this will cause the fetch server to use a different HTML simplifier that is more robust. If `node` is not available, the server falls back to the Python-only simplifier.
 
 ### Using uv (recommended)
 
@@ -193,6 +193,10 @@ environment variables (honoring `NO_PROXY`). Both `http(s)://` and SOCKS5 proxie
 installed with the server). A `socks://` proxy URL, as many desktop proxy settings export it, is treated as
 `socks5://`. A proxy setting the server cannot use makes each fetch fail with a tool error that says so.
 
+### Customization - HTML simplifier
+
+By default, the server uses the Node.js readability simplifier when `node` is available on `PATH`, and otherwise falls back to readabilipy's Python-only simplifier. If a host has Node.js installed but the readability path is slow or misconfigured, add `--no-readability-js` to force the Python-only simplifier.
+
 ## Windows Configuration
 
 If you're experiencing timeout issues on Windows, you may need to set the `PYTHONIOENCODING` environment variable to ensure proper character encoding:

src/fetch/src/mcp_server_fetch/__init__.py

@@ -21,6 +21,11 @@ def main():
         action="store_true",
         help="Allow fetching private, loopback and link-local addresses (refused by default)",
     )
+    parser.add_argument(
+        "--no-readability-js",
+        action="store_true",
+        help="Use readabilipy's Python-only HTML simplifier instead of the optional Node.js readability path",
+    )
 
     args = parser.parse_args()
     asyncio.run(
@@ -29,6 +34,7 @@ def main():
             args.ignore_robots_txt,
             args.proxy_url,
             args.allow_private_ips,
+            use_readability_js=False if args.no_readability_js else None,
         )
     )
 

src/fetch/src/mcp_server_fetch/server.py

@@ -1,6 +1,7 @@
 import asyncio
 import ipaddress
 import os
+import shutil
 import socket
 from typing import Annotated, Tuple
 from importlib.metadata import version
@@ -143,7 +144,7 @@ async def _refuse_private_destination(request: httpx.Request) -> None:
             )
 
 
-def extract_content_from_html(html: str) -> str:
+def extract_content_from_html(html: str, use_readability_js: bool | None = None) -> str:
     """Extract and convert HTML content to Markdown format.
 
     Args:
@@ -152,8 +153,11 @@ def extract_content_from_html(html: str) -> str:
     Returns:
         Simplified markdown version of the content
     """
+    if use_readability_js is None:
+        use_readability_js = shutil.which("node") is not None
+
     ret = readabilipy.simple_json.simple_json_from_html_string(
-        html, use_readability=True
+        html, use_readability=use_readability_js
     )
     failed = "<error>Page failed to be simplified from HTML</error>"
     if not ret["content"]:
@@ -302,6 +306,7 @@ async def fetch_url(
     force_raw: bool = False,
     proxy_url: str | None = None,
     allow_private_ips: bool = False,
+    use_readability_js: bool | None = None,
 ) -> Tuple[str, str]:
     """
     Fetch the URL and return the content in a form ready for the LLM, as well as a prefix string with status information.
@@ -338,7 +343,9 @@ async def fetch_url(
     )
 
     if is_page_html and not force_raw:
-        return extract_content_from_html(page_raw), ""
+        return extract_content_from_html(
+            page_raw, use_readability_js=use_readability_js
+        ), ""
 
     return (
         page_raw,
@@ -384,6 +391,7 @@ async def serve(
     ignore_robots_txt: bool = False,
     proxy_url: str | None = None,
     allow_private_ips: bool = False,
+    use_readability_js: bool | None = None,
 ) -> None:
     """Run the fetch MCP server.
 
@@ -458,6 +466,7 @@ async def call_tool(name, arguments: dict) -> list[TextContent]:
             force_raw=args.raw,
             proxy_url=proxy_url,
             allow_private_ips=allow_private_ips,
+            use_readability_js=use_readability_js,
         )
         original_length = len(content)
         if args.start_index >= original_length:
@@ -476,6 +485,7 @@ async def call_tool(name, arguments: dict) -> list[TextContent]:
             if actual_content_length == args.max_length and remaining_content > 0:
                 next_start = args.start_index + actual_content_length
                 content += f"\n\n<error>Content truncated. Call the fetch tool with a start_index of {next_start} to get more content.</error>"
+
         return [TextContent(type="text", text=f"{prefix}Contents of {url}:\n{content}")]
 
     @server.get_prompt()
@@ -495,6 +505,7 @@ async def get_prompt(name: str, arguments: dict | None) -> GetPromptResult:
                 user_agent_manual,
                 proxy_url=proxy_url,
                 allow_private_ips=allow_private_ips,
+                use_readability_js=use_readability_js,
             )
             # TODO: after SDK bug is addressed, don't catch the exception
         except McpError as e:

src/fetch/tests/test_entrypoints.py

@@ -31,7 +31,7 @@ def run_main(monkeypatch: pytest.MonkeyPatch, *argv: str) -> AsyncMock:
 
 def test_main_defaults(monkeypatch: pytest.MonkeyPatch) -> None:
     serve = run_main(monkeypatch)
-    serve.assert_awaited_once_with(None, False, None, False)
+    serve.assert_awaited_once_with(None, False, None, False, use_readability_js=None)
 
 
 def test_main_passes_every_flag(monkeypatch: pytest.MonkeyPatch) -> None:
@@ -43,9 +43,14 @@ def test_main_passes_every_flag(monkeypatch: pytest.MonkeyPatch) -> None:
         "--proxy-url",
         "http://proxy.example.com:8080",
         "--allow-private-ips",
+        "--no-readability-js",
     )
     serve.assert_awaited_once_with(
-        "MyBot/1.0", True, "http://proxy.example.com:8080", True
+        "MyBot/1.0",
+        True,
+        "http://proxy.example.com:8080",
+        True,
+        use_readability_js=False,
     )
 
 
@@ -62,6 +67,7 @@ def test_main_help_exits_zero(
         "--ignore-robots-txt",
         "--proxy-url",
         "--allow-private-ips",
+        "--no-readability-js",
     ):
         assert flag in out
 
@@ -90,7 +96,7 @@ def test_package_init_run_as_main_calls_main(monkeypatch: pytest.MonkeyPatch) ->
     monkeypatch.setattr(mcp_server_fetch.server, "serve", serve)
     monkeypatch.setattr(sys, "argv", ["mcp-server-fetch"])
     runpy.run_module("mcp_server_fetch.__init__", run_name="__main__")
-    serve.assert_awaited_once_with(None, False, None, False)
+    serve.assert_awaited_once_with(None, False, None, False, use_readability_js=None)
 
 
 def console_script() -> Path:

src/fetch/tests/test_protocol.py

@@ -21,6 +21,8 @@
 
 import httpx
 import pytest
+import readabilipy.simple_json
+from unittest.mock import patch
 from mcp import ClientSession
 from mcp.shared.exceptions import McpError
 from mcp.types import INVALID_PARAMS, CallToolResult
@@ -467,6 +469,24 @@ async def test_html_without_node_falls_back_to_pure_python(web: FakeWeb) -> None
     assert "https://example.com/x" not in text
 
 
+async def test_fetch_forwards_python_only_readability_choice(web: FakeWeb) -> None:
+    """serve(use_readability_js=False) reaches the extractor explicitly."""
+    web.add(ROBOTS, plain("", status=404))
+    web.add(PAGE, html(ARTICLE_HTML))
+    with patch(
+        "readabilipy.simple_json.simple_json_from_html_string",
+        wraps=readabilipy.simple_json.simple_json_from_html_string,
+    ) as spy:
+        async with connect(ignore_robots_txt=True, use_readability_js=False) as (
+            session,
+            _,
+        ):
+            result = await call(session, {"url": PAGE})
+    assert wire(result)["isError"] is False
+    spy.assert_called_once()
+    assert spy.call_args.kwargs["use_readability"] is False
+
+
 @pytest.mark.usefixtures("python_readability")
 async def test_empty_html_without_node_cannot_be_simplified(web: FakeWeb) -> None:
     # The pure-Python extractor returns "<div></div>" for an empty page, which

src/fetch/tests/test_server.py

@@ -8,6 +8,7 @@
 
 import httpx
 import pytest
+from unittest.mock import patch
 
 from mcp_server_fetch.server import (
     PROXY_ENV_VARS,
@@ -93,6 +94,35 @@ def test_empty_content_returns_error(self):
         result = extract_content_from_html(html)
         assert "<error>" in result
 
+    def test_can_disable_readability_js(self):
+        """Callers can force the Python-only extraction path."""
+        html = "<html><body><article><p>Hello World</p></article></body></html>"
+
+        with patch(
+            "readabilipy.simple_json.simple_json_from_html_string",
+            return_value={"content": "<p>Hello World</p>"},
+        ) as mock_extract:
+            result = extract_content_from_html(html, use_readability_js=False)
+
+        assert "Hello World" in result
+        mock_extract.assert_called_once_with(html, use_readability=False)
+
+    def test_auto_disables_readability_js_without_node(self):
+        """Python-only environments do not try the Node.js path."""
+        html = "<html><body><article><p>Hello World</p></article></body></html>"
+
+        with (
+            patch("shutil.which", return_value=None),
+            patch(
+                "readabilipy.simple_json.simple_json_from_html_string",
+                return_value={"content": "<p>Hello World</p>"},
+            ) as mock_extract,
+        ):
+            result = extract_content_from_html(html)
+
+        assert "Hello World" in result
+        mock_extract.assert_called_once_with(html, use_readability=False)
+
 
 class TestNormalizeProxyUrl:
     """Tests for normalize_proxy_url and normalize_proxy_env (#767)."""