DocsFetcher MCP Server

Implementation Reference

• src/index.ts:228-284 (registration)

  Registration of the 'fetch-library-docs' MCP tool, including input schema, description, and the complete inline handler function that resolves package URLs and fetches documentation.
  server.tool( "fetch-library-docs", { library: z .string() .describe( "Name of the package or URL of the library documentation to fetch" ), language: z .string() .optional() .describe( "Programming language or repository type if providing a package name (e.g., javascript, python, java, dotnet)" ), }, async ({ library, language = "javascript" }) => { console.error( `Fetching documentation for library: ${library} ${ language ? `(${language})` : "" }` ); try { // Determine if input is a URL or package name const isLibraryUrl = isUrl(library); let url = isLibraryUrl ? library : getPackageUrl(library, language); const documentationContent = await scraperService.fetchLibraryDocumentation(url); return { content: [ { type: "text", text: documentationContent, }, ], }; } catch (error) { console.error("Error fetching library documentation:", error); const errorMessage = `Error fetching library documentation: ${ error instanceof Error ? error.message : String(error) }`; return { content: [ { type: "text", text: errorMessage, }, ], isError: true, }; } } );
• src/services/ScraperService.ts:137-195 (handler)

  Key helper method invoked by the tool handler to perform the actual documentation fetching, crawling multiple pages, processing content with Cheerio, extracting code/API, compiling into Markdown, and adding LLM prompt instructions.
  public async fetchLibraryDocumentation( url: string, maxPages = 5 ): Promise<string> { try { // If input is not a URL, assume it's a package name if (!url.startsWith("http")) { url = `https://www.npmjs.com/package/${url}`; } // Extract library name from URL const libraryName = extractLibraryName(url); // Crawl documentation const pages = await this.crawlDocumentation(url, libraryName, maxPages); if (pages.length === 0) { throw new Error(`Failed to fetch documentation from ${url}`); } // Compile documentation into a single markdown document const documentation = this.compileDocumentation(pages, libraryName); // Include instructions for using the prompt const promptInstructions = ` --- 🔍 For better summarization, use the "summarize-library-docs" prompt with: - libraryName: "${libraryName}" - documentation: <the content above> Example: @summarize-library-docs with libraryName="${libraryName}" `; return documentation + promptInstructions; } catch (error) { console.error(`Error fetching URL content:`, error); // Extract library name from URL const libraryName = extractLibraryName(url); const errorMessage = `Error fetching URL content: ${ error instanceof Error ? error.message : String(error) }`; // Include error-specific prompt instructions const promptInstructions = ` --- 🔍 For information about this library despite the fetch error, use the "summarize-library-docs" prompt with: - libraryName: "${libraryName}" - errorStatus: "${error instanceof Error ? error.message : String(error)}" Example: @summarize-library-docs with libraryName="${libraryName}" and errorStatus="fetch failed" `; return errorMessage + promptInstructions; } }
• src/utils/packageRepository.ts:32-102 (helper)

  Utility function used in the tool handler to map package names to their respective repository documentation URLs based on programming language (npm, pypi, maven, nuget, etc.).
  export function getPackageUrl( packageName: string, language = "javascript" ): string { const lang = language.toLowerCase().trim(); switch (lang) { // JavaScript/TypeScript case "javascript": case "js": case "typescript": case "ts": case "node": case "nodejs": case "npm": return `https://www.npmjs.com/package/${packageName}`; // Python case "python": case "py": case "pypi": return `https://pypi.org/project/${packageName}`; // Java case "java": case "maven": return `https://mvnrepository.com/artifact/${packageName}`; // .NET case "dotnet": case ".net": case "csharp": case "c#": case "nuget": return `https://www.nuget.org/packages/${packageName}`; // Ruby case "ruby": case "gem": case "rubygem": case "rubygems": return `https://rubygems.org/gems/${packageName}`; // PHP case "php": case "composer": case "packagist": return `https://packagist.org/packages/${packageName}`; // Rust case "rust": case "cargo": case "crate": case "crates": return `https://crates.io/crates/${packageName}`; // Go case "go": case "golang": return `https://pkg.go.dev/${packageName}`; // Swift case "swift": case "cocoapods": return `https://cocoapods.org/pods/${packageName}`; // Default to npm default: return `https://www.npmjs.com/package/${packageName}`; } }
• src/utils/packageRepository.ts:8-14 (helper)

  Utility function used in the tool handler to check if the library input is a direct URL or a package name requiring URL resolution.
  export function isUrl(str: string): boolean { try { new URL(str); return true; } catch (e) { return false; }
• src/index.ts:230-242 (schema)

  Zod input schema defining the 'library' parameter (package name or URL) and optional 'language' for repository selection.
  { library: z .string() .describe( "Name of the package or URL of the library documentation to fetch" ), language: z .string() .optional() .describe( "Programming language or repository type if providing a package name (e.g., javascript, python, java, dotnet)" ), },