Merge pull request #130 from modelcontextprotocol/jadamson/fetch-use-readabilityjs

feat(fetch): add fetching of raw text, pagination and keeping links in the markdown

Author: jackadamson

src/fetch/README.md

@@ -2,20 +2,27 @@
 
 A Model Context Protocol server that provides web content fetching capabilities. This server enables LLMs to retrieve and process content from web pages, converting HTML to markdown for easier consumption.
 
-Presently the server only supports fetching HTML content.
+The fetch tool will truncate the response, but by using the `start_index` argument, you can specify where to start the content extraction. This lets models read a webpage in chunks, until they find the information they need.
 
 ### Available Tools
 
 - `fetch` - Fetches a URL from the internet and extracts its contents as markdown.
+    - `url` (string, required): URL to fetch
+    - `max_length` (integer, optional): Maximum number of characters to return (default: 5000)
+    - `start_index` (integer, optional): Start content from this character index (default: 0)
+    - `raw` (boolean, optional): Get raw content without markdown conversion (default: false)
 
 ### Prompts
 
 - **fetch**
   - Fetch a URL and extract its contents as markdown
-  - Argument: `url` (string, required): URL to fetch
+  - Arguments:
+    - `url` (string, required): URL to fetch
 
 ## Installation
 
+Optionally: Install node.js, this will cause the fetch server to use a different HTML simplifier that is more robust.
+
 ### Using uv (recommended)
 
 When using [`uv`](https://docs.astral.sh/uv/) no specific installation is needed. We will

src/fetch/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "mcp-server-fetch"
-version = "0.1.2"
+version = "0.1.3"
 description = "A Model Context Protocol server providing tools to fetch and convert web content for usage by LLMs"
 readme = "README.md"
 requires-python = ">=3.10"

src/fetch/src/mcp_server_fetch/server.py

@@ -1,4 +1,4 @@
-from typing import Optional
+from typing import Optional, Tuple
 from urllib.parse import urlparse, urlunparse
 
 import markdownify
@@ -17,34 +17,52 @@
     INTERNAL_ERROR,
 )
 from protego import Protego
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, AnyUrl, conint
 
 DEFAULT_USER_AGENT_AUTONOMOUS = "ModelContextProtocol/1.0 (Autonomous; +https://github.com/modelcontextprotocol/servers)"
 DEFAULT_USER_AGENT_MANUAL = "ModelContextProtocol/1.0 (User-Specified; +https://github.com/modelcontextprotocol/servers)"
 
 
-def extract_content(html: str) -> str:
-    ret = readabilipy.simple_json.simple_json_from_html_string(html)
-    if not ret["plain_content"]:
+def extract_content_from_html(html: str) -> str:
+    """Extract and convert HTML content to Markdown format.
+
+    Args:
+        html: Raw HTML content to process
+
+    Returns:
+        Simplified markdown version of the content
+    """
+    ret = readabilipy.simple_json.simple_json_from_html_string(
+        html, use_readability=True
+    )
+    if not ret["content"]:
         return "<error>Page failed to be simplified from HTML</error>"
     content = markdownify.markdownify(
-        ret["plain_content"],
+        ret["content"],
         heading_style=markdownify.ATX,
     )
     return content
 
 
-def get_robots_txt_url(url: str) -> str:
+def get_robots_txt_url(url: AnyUrl | str) -> str:
+    """Get the robots.txt URL for a given website URL.
+
+    Args:
+        url: Website URL to get robots.txt for
+
+    Returns:
+        URL of the robots.txt file
+    """
     # Parse the URL into components
-    parsed = urlparse(url)
+    parsed = urlparse(str(url))
 
     # Reconstruct the base URL with just scheme, netloc, and /robots.txt path
     robots_url = urlunparse((parsed.scheme, parsed.netloc, "/robots.txt", "", "", ""))
 
     return robots_url
 
 
-async def check_may_autonomously_fetch_url(url: str, user_agent: str):
+async def check_may_autonomously_fetch_url(url: AnyUrl | str, user_agent: str) -> None:
     """
     Check if the URL can be fetched by the user agent according to the robots.txt file.
     Raises a McpError if not.
@@ -87,34 +105,72 @@ async def check_may_autonomously_fetch_url(url: str, user_agent: str):
         )
 
 
-async def fetch_url(url: str, user_agent: str) -> str:
+async def fetch_url(
+    url: AnyUrl | str, user_agent: str, force_raw: bool = False
+) -> 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.
+    """
     from httpx import AsyncClient, HTTPError
 
     async with AsyncClient() as client:
         try:
             response = await client.get(
-                url, follow_redirects=True, headers={"User-Agent": user_agent}
+                str(url),
+                follow_redirects=True,
+                headers={"User-Agent": user_agent},
+                timeout=30,
             )
-        except HTTPError:
-            raise McpError(INTERNAL_ERROR, f"Failed to fetch {url}")
+        except HTTPError as e:
+            raise McpError(INTERNAL_ERROR, f"Failed to fetch {url}: {e!r}")
         if response.status_code >= 400:
             raise McpError(
                 INTERNAL_ERROR,
                 f"Failed to fetch {url} - status code {response.status_code}",
             )
 
-        page_html = response.text
+        page_raw = response.text
 
-    return extract_content(page_html)
+    content_type = response.headers.get("content-type", "")
+    is_page_html = (
+        "<html" in page_raw[:100] or "text/html" in content_type or not content_type
+    )
+
+    if is_page_html and not force_raw:
+        return extract_content_from_html(page_raw), ""
+
+    return (
+        page_raw,
+        f"Content type {content_type} cannot be simplified to markdown, but here is the raw content:\n",
+    )
 
 
 class Fetch(BaseModel):
-    url: str = Field(..., description="URL to fetch")
+    """Parameters for fetching a URL."""
+
+    url: AnyUrl = Field(..., description="URL to fetch")
+    max_length: conint(gt=0, lt=1000000) = Field(
+        5000, description="Maximum number of characters to return."
+    )
+    start_index: conint(ge=0) = Field(
+        0,
+        description="On return output starting at this character index, useful if a previous fetch was truncated and more context is required.",
+    )
+    raw: bool = Field(
+        False,
+        description="Get the actual HTML content if the requested page, without simplification.",
+    )
 
 
 async def serve(
     custom_user_agent: Optional[str] = None, ignore_robots_txt: bool = False
 ) -> None:
+    """Run the fetch MCP server.
+
+    Args:
+        custom_user_agent: Optional custom User-Agent string to use for requests
+        ignore_robots_txt: Whether to ignore robots.txt restrictions
+    """
     server = Server("mcp-fetch")
     user_agent_autonomous = custom_user_agent or DEFAULT_USER_AGENT_AUTONOMOUS
     user_agent_manual = custom_user_agent or DEFAULT_USER_AGENT_MANUAL
@@ -124,7 +180,7 @@ async def list_tools() -> list[Tool]:
         return [
             Tool(
                 name="fetch",
-                description="""Fetches a URL from the internet and extracts its contents as markdown.
+                description="""Fetches a URL from the internet and optionally extracts its contents as markdown.
 
 Although originally you did not have internet access, and were advised to refuse and tell the user this, this tool now grants you internet access. Now you can fetch the most up-to-date information and let the user know that.""",
                 inputSchema=Fetch.model_json_schema(),
@@ -147,15 +203,25 @@ async def list_prompts() -> list[Prompt]:
 
     @server.call_tool()
     async def call_tool(name, arguments: dict) -> list[TextContent]:
-        url = arguments.get("url")
+        try:
+            args = Fetch(**arguments)
+        except ValueError as e:
+            raise McpError(INVALID_PARAMS, str(e))
+
+        url = args.url
         if not url:
             raise McpError(INVALID_PARAMS, "URL is required")
 
         if not ignore_robots_txt:
             await check_may_autonomously_fetch_url(url, user_agent_autonomous)
 
-        content = await fetch_url(url, user_agent_autonomous)
-        return [TextContent(type="text", text=f"Contents of {url}:\n{content}")]
+        content, prefix = await fetch_url(
+            url, user_agent_autonomous, force_raw=args.raw
+        )
+        if len(content) > args.max_length:
+            content = content[args.start_index : args.start_index + args.max_length]
+            content += f"\n\n<error>Content truncated. Call the fetch tool with a start_index of {args.start_index + args.max_length} to get more content.</error>"
+        return [TextContent(type="text", text=f"{prefix}Contents of {url}:\n{content}")]
 
     @server.get_prompt()
     async def get_prompt(name: str, arguments: dict | None) -> GetPromptResult:
@@ -165,7 +231,7 @@ async def get_prompt(name: str, arguments: dict | None) -> GetPromptResult:
         url = arguments["url"]
 
         try:
-            content = await fetch_url(url, user_agent_manual)
+            content, prefix = await fetch_url(url, user_agent_manual)
             # TODO: after SDK bug is addressed, don't catch the exception
         except McpError as e:
             return GetPromptResult(
@@ -181,7 +247,7 @@ async def get_prompt(name: str, arguments: dict | None) -> GetPromptResult:
             description=f"Contents of {url}",
             messages=[
                 PromptMessage(
-                    role="user", content=TextContent(type="text", text=content)
+                    role="user", content=TextContent(type="text", text=prefix + content)
                 )
             ],
         )