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ESnark

Vite MCP Server

by ESnark
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TypeScript
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get-console-logs

Retrieve console logs from the Vite development server. Optionally filter by checkpoint or limit to recent logs for debugging and monitoring.

Instructions

Retrieves console logs from the development server

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
checkpointNoIf specified, returns only logs recorded at this checkpoint
limitNoNumber of logs to return, starting from the most recent log

Implementation Reference

  • src/tools/browser-tools.ts:709-756 (handler)
    The actual tool handler for 'get-console-logs'. It reads logs using LogManager.readLogs(), parses them from JSON, and returns them with write position and total log count.
    // Console logs retrieval tool
server.tool(
  'get-console-logs',
  'Retrieves console logs from the development server',
  {
    checkpoint: z.string().optional().describe('If specified, returns only logs recorded at this checkpoint'),
    limit: z.number().optional().describe('Number of logs to return, starting from the most recent log')
  },
  async ({ checkpoint, limit = 100 }) => {
    try {
      // Read logs (always provide limit value)
      const result = await logManager.readLogs(limit, checkpoint);

      // Parse logs
      const parsedLogs = result.logs.map((log: string) => {
        try {
          return JSON.parse(log);
        } catch (error) {
          return { type: 'unknown', text: log, timestamp: new Date().toISOString() };
        }
      });

      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify({
              logs: parsedLogs,
              writePosition: result.writePosition,
              totalLogs: result.totalLogs
            }, null, 2)
          }
        ]
      };
    } catch (error) {
      Logger.error(`Failed to read console logs: ${error}`);
      return {
        content: [
          {
            type: 'text',
            text: `Failed to read console logs: ${error}`
          }
        ],
        isError: true
      };
    }
  }
);
  • src/tools/browser-tools.ts:712-716 (schema)
    Input schema for 'get-console-logs' tool: optional 'checkpoint' (string) to filter by checkpoint ID, and optional 'limit' (number, default 100) for number of logs to return.
    'Retrieves console logs from the development server',
{
  checkpoint: z.string().optional().describe('If specified, returns only logs recorded at this checkpoint'),
  limit: z.number().optional().describe('Number of logs to return, starting from the most recent log')
},
  • src/tools/browser-tools.ts:709-756 (registration)
    The tool is registered inside registerBrowserTools() using server.tool('get-console-logs', ...) in src/tools/browser-tools.ts, which is called from src/index.ts at line 87.
    // Console logs retrieval tool
server.tool(
  'get-console-logs',
  'Retrieves console logs from the development server',
  {
    checkpoint: z.string().optional().describe('If specified, returns only logs recorded at this checkpoint'),
    limit: z.number().optional().describe('Number of logs to return, starting from the most recent log')
  },
  async ({ checkpoint, limit = 100 }) => {
    try {
      // Read logs (always provide limit value)
      const result = await logManager.readLogs(limit, checkpoint);

      // Parse logs
      const parsedLogs = result.logs.map((log: string) => {
        try {
          return JSON.parse(log);
        } catch (error) {
          return { type: 'unknown', text: log, timestamp: new Date().toISOString() };
        }
      });

      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify({
              logs: parsedLogs,
              writePosition: result.writePosition,
              totalLogs: result.totalLogs
            }, null, 2)
          }
        ]
      };
    } catch (error) {
      Logger.error(`Failed to read console logs: ${error}`);
      return {
        content: [
          {
            type: 'text',
            text: `Failed to read console logs: ${error}`
          }
        ],
        isError: true
      };
    }
  }
);
  • src/tools/log-manager.ts:199-300 (helper)
    The LogManager.readLogs() helper method that reads logs from files, supporting filtering by checkpoint ID and limiting the number of logs returned.
    public async readLogs(limit: number, checkpointId?: string): Promise<{ logs: string[], writePosition: number, totalLogs: number }> {
  try {
    // 1. Calculate necessary information
    const logDir = path.dirname(this.getLogFilePath(0, checkpointId));
    const filePattern = checkpointId ?
      new RegExp(`^chk-${checkpointId}-(\\d+)\\.log$`) :
      /^default-log-(\d+)\.log$/;

    // 2. Find log files in directory
    const files = fs.existsSync(logDir) ? fs.readdirSync(logDir) : [];
    const logFiles = files
      .filter(file => filePattern.test(file))
      .map(file => {
        const match = file.match(filePattern);
        return {
          file,
          path: path.join(logDir, file),
          number: match ? parseInt(match[1], 10) : -1
        };
      })
      .filter(item => item.number >= 0)
      .sort((a, b) => a.number - b.number); // Sort in order (oldest first)

    if (logFiles.length === 0) {
      return { logs: [], writePosition: 0, totalLogs: 0 };
    }

    // 3. Calculate total number of logs (completed files + current file log count)
    const lastFileIndex = logFiles.length - 1;
    const completedFilesLogs = lastFileIndex * this.MAX_LOGS_PER_FILE;

    // Get log count of the last file
    let currentFileLogCount = 0;
    if (checkpointId) {
      const checkpointData = this.checkpointStreams.get(checkpointId);
      currentFileLogCount = checkpointData ? checkpointData.currentLogCount : 0;
    } else {
      currentFileLogCount = this.currentLogCount;
    }

    const totalLogs = completedFilesLogs + currentFileLogCount;

    // 4. Return empty result if no logs needed
    if (totalLogs === 0) {
      return { logs: [], writePosition: currentFileLogCount, totalLogs: 0 };
    }

    // 5. Calculate start position and number of logs to read
    const startPosition = Math.max(0, totalLogs - limit);
    const startFileIndex = Math.floor(startPosition / this.MAX_LOGS_PER_FILE);
    const startLogInFile = startPosition % this.MAX_LOGS_PER_FILE;

    // 6. Read log files (using stream)
    const logs: string[] = [];
    let logsNeeded = Math.min(limit, totalLogs);

    for (let i = startFileIndex; i < logFiles.length && logsNeeded > 0; i++) {
      const filePath = logFiles[i].path;
      if (!fs.existsSync(filePath)) continue;

      // Read line by line using readline interface
      const rl = readline.createInterface({
        input: fs.createReadStream(filePath, { encoding: 'utf-8' }),
        crlfDelay: Infinity
      });

      let skippedLines = 0;

      // Skip lines if this is the first file and has a start position
      const shouldSkipLines = (i === startFileIndex && startLogInFile > 0);
      const linesToSkip = shouldSkipLines ? startLogInFile : 0;

      for await (const line of rl) {
        if (!line.trim()) continue;

        // Skip necessary lines
        if (shouldSkipLines && skippedLines < linesToSkip) {
          skippedLines++;
          continue;
        }

        logs.push(line);
        logsNeeded--;

        if (logsNeeded <= 0) {
          rl.close();
          break;
        }
      }
    }

    // 7. Return result
    return {
      logs,
      writePosition: currentFileLogCount,
      totalLogs
    };
  } catch (error) {
    Logger.error(`Failed to read logs: ${error}`);
    return { logs: [], writePosition: 0, totalLogs: 0 };
  }
}
  • src/tools/log-manager.ts:137-197 (helper)
    The LogManager.appendLog() helper method that writes console log entries to both default and checkpoint-specific log files.
    public async appendLog(logEntry: string, checkpointId?: string): Promise<void> {
  try {
    // Append log to default log file
    await new Promise<void>((resolve, reject) => {
      const writeStream = this.writeStream;

      if (!writeStream) {
        reject(new Error('Log file is not initialized'));
        return;
      }

      this.writeStream?.write(logEntry, (err: Error | null | undefined) => {
        if (err) { reject(err); } else {
          this.currentLogCount++;

          if (this.currentLogCount >= this.MAX_LOGS_PER_FILE) {
            this.initializeLogFile({ nextFileNumber: this.currentFileNumber + 1 });
          }

          resolve();
        }
      });
    });

    // Append log to checkpoint log file
    if (checkpointId) {
      if (!this.checkpointStreams.has(checkpointId)) {
        this.initializeLogFile({ checkpointId });
      } else if (this.isCheckpointStreamAttached(checkpointId) === false) {
        await this.attachCheckpointStream(checkpointId);
      }

      await this.detachCheckpointStreams();
    }

    if (checkpointId) {
      await new Promise<void>((resolve, reject) => {
        const streamData = this.checkpointStreams.get(checkpointId);

        if (!streamData) {
          reject(new Error('Checkpoint stream data not found'));
          return;
        }

        streamData.writeStream?.write(logEntry, (err: Error | null | undefined) => {
          if (err) { reject(err); } else {
            streamData.currentLogCount++;

            if (streamData.currentLogCount >= this.MAX_LOGS_PER_FILE) {
              this.initializeLogFile({ nextFileNumber: streamData.currentFileNumber + 1, checkpointId });
            }

            resolve();
          }
        });
      });
    }
  } catch (error) {
    Logger.error(`Failed to append log: ${error}`);
  }
}

Tool Definition Quality

C2.9/5.0
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations provided, so the description must disclose behavior. It only states the core function without explaining what happens with omitted parameters, output format, pagination, or side effects (e.g., whether logs are cleared).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single sentence with no wasted words. However, front-loading is not an issue, but it could be slightly more informative without sacrificing conciseness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given optional parameters and no output schema, the description should clarify default behavior (e.g., returns recent logs when no filters). It lacks information about return format and limits.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% (both parameters have descriptions). The description adds no additional meaning beyond the schema, so baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action (retrieves) and resource (console logs from the development server). It distinguishes the tool's purpose from siblings like get-hmr-events, but does not explicitly differentiate from all siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance on when to use this tool versus alternatives such as get-hmr-events. The description does not mention prerequisites, scenarios, or exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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