ADB MCP Server

Implementation Reference

• src/index.ts:536-566 (handler)

  The core handler function for the 'adb_logcat' tool. It processes input arguments for device, filter, and lines; constructs the adb logcat command; executes it using runAdb; limits the output to the specified number of lines; and returns the log content or error.

  async (args: z.infer<typeof AdbLogcatSchema>, _extra: RequestHandlerExtra) => {
    const lines = args.lines || 50;
    const filterExpr = args.filter ? args.filter : "";
    log(LogLevel.INFO, `Reading logcat (${lines} lines, filter: ${filterExpr || 'none'})`);
    
    const deviceArgs = buildDeviceArgs(args.device);
    const filterArgs = filterExpr ? splitCommandArguments(filterExpr) : [];
    const adbArgs = [...deviceArgs, "logcat", "-d", ...filterArgs];
  
    try {
      const { stdout, stderr } = await runAdb(adbArgs);
      if (stderr) {
        log(LogLevel.WARN, `logcat returned stderr: ${stderr}`);
      }
  
      const logLines = stdout.split(/\r?\n/);
      const limitedLines = lines > 0 ? logLines.slice(-lines) : logLines;
      const text = limitedLines.join("\n");
  
      return {
        content: [{ type: "text" as const, text }]
      };
    } catch (error) {
      const errorMsg = error instanceof Error ? error.message : String(error);
      log(LogLevel.ERROR, `Error reading logcat: ${errorMsg}`);
      return {
        content: [{ type: "text" as const, text: `Error reading logcat: ${errorMsg}` }],
        isError: true
      };
    }
  },

• src/index.ts:533-568 (registration)

  Registers the 'adb_logcat' tool with the MCP server via server.tool(), specifying the tool name, input schema shape, inline handler function, and tool description.

  server.tool(
    "adb_logcat",
    AdbLogcatSchema.shape,
    async (args: z.infer<typeof AdbLogcatSchema>, _extra: RequestHandlerExtra) => {
      const lines = args.lines || 50;
      const filterExpr = args.filter ? args.filter : "";
      log(LogLevel.INFO, `Reading logcat (${lines} lines, filter: ${filterExpr || 'none'})`);
      
      const deviceArgs = buildDeviceArgs(args.device);
      const filterArgs = filterExpr ? splitCommandArguments(filterExpr) : [];
      const adbArgs = [...deviceArgs, "logcat", "-d", ...filterArgs];
  
      try {
        const { stdout, stderr } = await runAdb(adbArgs);
        if (stderr) {
          log(LogLevel.WARN, `logcat returned stderr: ${stderr}`);
        }
  
        const logLines = stdout.split(/\r?\n/);
        const limitedLines = lines > 0 ? logLines.slice(-lines) : logLines;
        const text = limitedLines.join("\n");
  
        return {
          content: [{ type: "text" as const, text }]
        };
      } catch (error) {
        const errorMsg = error instanceof Error ? error.message : String(error);
        log(LogLevel.ERROR, `Error reading logcat: ${errorMsg}`);
        return {
          content: [{ type: "text" as const, text: `Error reading logcat: ${errorMsg}` }],
          isError: true
        };
      }
    },
    { description: ADB_LOGCAT_TOOL_DESCRIPTION }
  );

• src/types.ts:56-60 (schema)

  Defines the raw input schema object for adb_logcat parameters using Zod primitives with descriptions and defaults.

  export const adbLogcatInputSchema = {
    filter: z.string().optional().describe("Logcat filter expression (optional)"),
    device: z.string().optional().describe("Specific device ID (optional)"),
    lines: z.number().optional().default(50).describe("Number of lines to return (default: 50)")
  };

• src/types.ts:105-105 (schema)

  Creates the full Zod schema for adb_logcat by wrapping the input schema with z.object() for validation.

  export const AdbLogcatSchema = z.object(adbLogcatInputSchema);

• src/index.ts:113-120 (helper)

  Tool description string used in registration for the adb_logcat tool, providing usage guidance.

   * Tool description for adb-logcat
   */
  const ADB_LOGCAT_TOOL_DESCRIPTION = 
    "Retrieves Android system and application logs from a connected device. " +
    "Ideal for debugging app behavior, monitoring system events, and identifying errors. " +
    "Supports filtering by log tags or expressions to narrow down relevant information. " +
    "Results can be limited to a specific number of lines, making it useful for both brief checks and detailed analysis. " +
    "Use when troubleshooting crashes, unexpected behavior, or performance issues.";