Stimulus Docs MCP Server

Instructions

Implementation Reference

• src/index.ts:21-44 (handler)

  Handler function for the 'handbook-hello' tool (shared pattern): fetches markdown content via readMarkdownFile(path.join('handbook', '02_hello_stimulus.md')) and returns it as MCP content block or error message.

    async () => {
      try {
        const content = await readMarkdownFile(path.join(folder, file));
        return {
          content: [
            {
              type: "text",
              text: content
            }
          ]
        };
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return {
          content: [
            {
              type: "text",
              text: `Error reading ${file}: ${errorMessage}`
            }
          ]
        };
      }
    }
  );

• src/config.ts:27-32 (schema)

  Schema/configuration entry in docFiles array defining the tool name 'handbook-hello', its markdown source file, folder, and description.

  {
    folder: 'handbook',
    file: '02_hello_stimulus.md',
    name: 'handbook-hello',
    description: 'Step-by-step tutorial for building your first Stimulus controller - covers creating a greeting controller with targets, actions, and DOM event handling'
  },

• src/index.ts:17-45 (registration)

  Registration of the 'handbook-hello' tool (via loop over docFiles) on the MCP server using server.tool(name, description, handlerFn).

  docFiles.forEach(({ folder, file, name, description }) => {
    server.tool(
      name,
      description,
      async () => {
        try {
          const content = await readMarkdownFile(path.join(folder, file));
          return {
            content: [
              {
                type: "text",
                text: content
              }
            ]
          };
        } catch (error) {
          const errorMessage = error instanceof Error ? error.message : String(error);
          return {
            content: [
              {
                type: "text",
                text: `Error reading ${file}: ${errorMessage}`
              }
            ]
          };
        }
      }
    );
  });

• src/documentReader.ts:14-61 (helper)

  Supporting function implementing file reading logic (cache → GitHub → local fallback) for the tool's markdown file.

  export async function readMarkdownFile(filename: string): Promise<string> {
    const filePath = path.join(docsFolder, filename);
    if (!filePath.startsWith(docsFolder)) {
      throw new Error("Invalid file path");
    }
    
    // Get current commit info if we don't have it yet
    if (!mainBranchInfo) {
      try {
        const commitInfo = await fetchMainBranchInformation();
        const cacheKey = `${commitInfo.sha.substring(0, 7)}-${commitInfo.timestamp}`;
        mainBranchInfo = {
          ...commitInfo,
          cacheKey
        };
      } catch (shaError) {
        console.error('Failed to get GitHub commit info, falling back to direct fetch');
      }
    }
    
    // Try to read from cache first if we have commit info
    if (mainBranchInfo) {
      const cachedFilePath = path.join(cacheFolder, mainBranchInfo.cacheKey, filename);
      try {
        const content = await fs.promises.readFile(cachedFilePath, "utf-8");
        console.error(`Using cached content for ${mainBranchInfo.cacheKey}: ${filename}`);
        return content;
      } catch (cacheError) {
        // Cache miss, continue to fetch from GitHub
      }
    }
    
    // Fetch from GitHub
    try {
      return await fetchFromGitHub(filename, mainBranchInfo?.cacheKey);
    } catch (githubError) {
      console.error(`GitHub fetch failed: ${githubError}, attempting to read from local files...`);
      
      // Fallback: read from local files
      try {
        return await fs.promises.readFile(filePath, "utf-8");
      } catch (localError) {
        const githubErrorMessage = githubError instanceof Error ? githubError.message : String(githubError);
        const localErrorMessage = localError instanceof Error ? localError.message : String(localError);
        throw new Error(`Failed to read file from GitHub (${githubErrorMessage}) and locally (${localErrorMessage})`);
      }
    }
  }