DocsFetcher MCP Server

Implementation Reference

• src/index.ts:174-225 (registration)

  Registration of the 'fetch-package-docs' MCP tool, including Zod input schema (packageName, optional language) and inline async handler that resolves package URL and fetches/compiles documentation.
  server.tool( "fetch-package-docs", { packageName: z .string() .describe("Name of the package to fetch documentation for"), language: z .string() .optional() .describe( "Programming language or repository type (e.g., javascript, python, java, dotnet)" ), }, async ({ packageName, language = "javascript" }) => { console.error( `Fetching documentation for package: ${packageName} (${language})` ); try { const packageUrl = getPackageUrl(packageName, language); console.error(`Using package URL: ${packageUrl}`); const documentationContent = await scraperService.fetchLibraryDocumentation(packageUrl); return { content: [ { type: "text", text: documentationContent, }, ], }; } catch (error) { console.error("Error fetching package content:", error); const errorMessage = `Error fetching package documentation: ${ error instanceof Error ? error.message : String(error) }`; return { content: [ { type: "text", text: errorMessage, }, ], isError: true, }; } } );
• src/utils/packageRepository.ts:32-102 (helper)

  Helper function getPackageUrl that maps package name and language to the corresponding package registry documentation URL (npm, pypi, nuget, etc.). Called in the handler.
  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/services/ScraperService.ts:137-195 (helper)

  Core helper method in ScraperService that crawls the given URL, extracts and compiles documentation into markdown, adds prompts for summarization. Invoked by the tool handler.
  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; } }