mcp-nixos

Instructions

Implementation Reference

• mcp_nixos/server.py:689-739 (handler)

  The main handler function for the 'home_manager_info' tool. It parses Home Manager HTML documentation to retrieve detailed information about a specific configuration option, including type and description, with fallback suggestions if not found exactly.
  @mcp.tool() async def home_manager_info(name: str) -> str: """Get detailed information about a specific Home Manager option. Requires an exact option name match. If not found, suggests similar options. Args: name: The exact option name (e.g., 'programs.git.enable') Returns: Plain text with option details (name, type, description) or error with suggestions """ try: # Search more broadly first options = parse_html_options(HOME_MANAGER_URL, name, "", 100) # Look for exact match for opt in options: if opt["name"] == name: info = [] info.append(f"Option: {name}") if opt["type"]: info.append(f"Type: {opt['type']}") if opt["description"]: info.append(f"Description: {opt['description']}") return "\n".join(info) # If not found, check if there are similar options to suggest if options: suggestions = [] for opt in options[:5]: # Show up to 5 suggestions if name in opt["name"] or opt["name"].startswith(name + "."): suggestions.append(opt["name"]) if suggestions: return error( f"Option '{name}' not found. Did you mean one of these?\n" + "\n".join(f" • {s}" for s in suggestions) + f"\n\nTip: Use home_manager_options_by_prefix('{name}') to browse all options with this prefix.", "NOT_FOUND", ) return error( f"Option '{name}' not found.\n" + f"Tip: Use home_manager_options_by_prefix('{name}') to browse available options.", "NOT_FOUND", ) except Exception as e: return error(str(e))
• mcp_nixos/server.py:247-336 (helper)

  Core helper function that parses HTML documentation from Home Manager (and other) sites to extract option names, types, and descriptions. Used by home_manager_info and related search tools.
  def parse_html_options(url: str, query: str = "", prefix: str = "", limit: int = 100) -> list[dict[str, str]]: """Parse options from HTML documentation.""" try: resp = requests.get(url, timeout=30) # Increase timeout for large docs resp.raise_for_status() # Use resp.content to let BeautifulSoup handle encoding detection # This prevents encoding errors like "unknown encoding: windows-1252" soup = BeautifulSoup(resp.content, "html.parser") options = [] # Get all dt elements dts = soup.find_all("dt") for dt in dts: # Get option name name = "" if "home-manager" in url: # Home Manager uses anchor IDs like "opt-programs.git.enable" anchor = dt.find("a", id=True) if anchor: anchor_id = anchor.get("id", "") # Remove "opt-" prefix and convert underscores if anchor_id.startswith("opt-"): name = anchor_id[4:] # Remove "opt-" prefix # Convert _name_ placeholders back to <name> name = name.replace("_name_", "<name>") else: # Fallback to text content name_elem = dt.find(string=True, recursive=False) if name_elem: name = name_elem.strip() else: name = dt.get_text(strip=True) else: # Darwin and fallback - use text content name = dt.get_text(strip=True) # Skip if it doesn't look like an option (must contain a dot) # But allow single-word options in some cases if "." not in name and len(name.split()) > 1: continue # Filter by query or prefix if query and query.lower() not in name.lower(): continue if prefix and not (name.startswith(prefix + ".") or name == prefix): continue # Find the corresponding dd element dd = dt.find_next_sibling("dd") if dd: # Extract description (first p tag or direct text) desc_elem = dd.find("p") if desc_elem: description = desc_elem.get_text(strip=True) else: # Get first text node, handle None case text = dd.get_text(strip=True) description = text.split("\n")[0] if text else "" # Extract type info - look for various patterns type_info = "" # Pattern 1: <span class="term">Type: ...</span> type_elem = dd.find("span", class_="term") if type_elem and "Type:" in type_elem.get_text(): type_info = type_elem.get_text(strip=True).replace("Type:", "").strip() # Pattern 2: Look for "Type:" in text elif "Type:" in dd.get_text(): text = dd.get_text() type_start = text.find("Type:") + 5 type_end = text.find("\n", type_start) if type_end == -1: type_end = len(text) type_info = text[type_start:type_end].strip() options.append( { "name": name, "description": description[:200] if len(description) > 200 else description, "type": type_info, } ) if len(options) >= limit: break return options except Exception as exc: raise DocumentParseError(f"Failed to fetch docs: {str(exc)}") from exc
• mcp_nixos/server.py:689-689 (registration)

  The @mcp.tool() decorator registers the home_manager_info function as an MCP tool.
  @mcp.tool()