Playwright MCP Server

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

Annotations indicate destructiveHint=true and readOnlyHint=false, suggesting this tool can modify the page. The description adds value by specifying that it evaluates expressions 'on page or element', which clarifies the scope beyond what annotations provide. However, it doesn't detail potential side effects like page reloads or security implications, leaving some behavioral aspects uncovered.

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

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

The description is a single, front-loaded sentence that directly states the tool's function without unnecessary words. It efficiently communicates the core purpose, making it highly concise and well-structured.

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

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

Given the complexity of a JavaScript evaluation tool with destructive annotations and no output schema, the description is minimal. It covers the basic purpose but lacks details on return values, error handling, or security considerations, which are important for such a powerful tool. This leaves gaps in contextual understanding.

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

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

Schema description coverage is 100%, so the input schema fully documents the parameters. The description adds no additional meaning beyond the schema, such as examples of valid expressions or interaction patterns. Baseline score of 3 is appropriate as the schema handles the heavy lifting.

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

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

The description clearly states the verb 'evaluate' and the resource 'JavaScript expression on page or element', which is specific and actionable. However, it doesn't explicitly differentiate from sibling tools like browser_run_code, which might have overlapping functionality, preventing a perfect score.

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

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

The description provides no guidance on when to use this tool versus alternatives like browser_run_code or other browser interaction tools. It lacks context about scenarios where evaluating JavaScript is preferred over other methods, offering minimal usage direction.

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