Loading ToolBench
Collection of Model Context Protocol (MCP) servers for software testing tools and quality assurance
This Playwright MCP server has clear tool definitions with consistently present descriptions and properly formatted input schemas. All 8 tools are explicitly registered with type-safe enums and constraints. Naming follows verb_noun convention (launch_browser, get_page_content, perform_action). However, descriptions are functional but brief (avg ~90 chars), lacking the 50-200 char sweet spot and missing key context about WHEN to use each tool, dependencies between tools, and recovery guidance for errors. Output schemas are not documented at all, LLMs cannot reason about return values. Error handling exists (errorReporting=true) but with no visible guidance text. Some parameter descriptions lack actionable constraints (e.g., 'JavaScript code' without safety guardrails). Overall, definitions are competent but below production A-grade due to missing output documentation and thin descriptions.
Capture a screenshot of the current page. Returns base64 encoded image.
Close a browser session and clean up resources.
Execute Playwright code in the current browser context. Useful for complex interactions.
Get the current page DOM content, title, URL, and other metadata.
Launch a browser instance and navigate to a URL. Returns a session ID for subsequent operations.
List all active browser sessions.
Perform an action on a page element (click, fill, select, etc.)
No output schemas documented. LLMs cannot infer what fields tools return, forcing blind reasoning and preventing chaining of tool calls. E.g., launch_browser returns a session_id, but this is not formally declared.
execute_test_script accepts arbitrary JavaScript code with no safety guardrails or sanitization guidance. Description lacks constraints: 'JavaScript code to execute in the browser context' is too permissive. No mention of code injection risks or LLM prompt injection mitigations.
Descriptions are functional but thin (avg 67 chars, baseline 194 chars for A-grade tools). Missing context about WHEN to use each tool vs alternatives. E.g., 'Get the current page DOM content...' does not explain when to call this vs capture_screenshot, or that it requires launch_browser first.
| Scored | Grade | Overall | Spec posture | Rubric |
|---|---|---|---|---|
| 2026-09-22 | D | 57 | 2026-07-28+ | v2 |
| 2026-03-09 | F | 0 | - | v1 |
Execute a Playwright test file and return the results.
run_test_file accepts 'file_path' parameter with no validation constraints. Description lacks format guidance (absolute vs relative paths, allowed directories, file extensions). LLMs may pass unsafe paths (e.g., ../../../etc/passwd).
perform_action has interdependent parameters: 'value' only applies to fill/select, 'key' only to press action. Documentation does not state these relationships, leaving LLMs to guess which params are required for each action variant.
Error handling present (errorReporting=true) but no error response format visible. No guidance on how tools communicate retryable vs fatal errors, or what recovery actions LLMs should take. Patterns like 'recovery-guide' not evident in code.
Session management requires manual tracking of session_id across tool calls. No implicit session context or session lifecycle hooks visible. LLMs must remember IDs and pass them correctly, brittle chain requires tool annotations or prompt engineering.