Cloudflare Playwright MCP

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

Annotations indicate readOnlyHint=false, openWorldHint=true, and destructiveHint=true, covering key behavioral traits. The description adds context by specifying 'on page or element', which clarifies scope but doesn't elaborate on risks (e.g., potential page crashes from code) or auth needs. It doesn't contradict annotations, but adds minimal value beyond them.

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, efficient sentence with zero waste. It's front-loaded with the core action and resource, making it easy to parse quickly. Every word earns its place by conveying essential information without redundancy.

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 tool's complexity (JavaScript evaluation with destructive potential), annotations cover safety traits, but there's no output schema. The description lacks details on return values, error handling, or execution context. It's minimally adequate but leaves gaps for a tool that could have significant side effects.

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%, providing clear parameter details. The description mentions 'page or element', hinting at the optional 'element' or 'ref' parameters, but adds no syntax or format details beyond the schema. With high schema coverage, the baseline score of 3 is appropriate as the description doesn't significantly enhance parameter understanding.

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 'Evaluate JavaScript expression on page or element' clearly states the verb 'evaluate' and resource 'JavaScript expression', specifying it can target 'page or element'. It distinguishes from siblings like browser_click or browser_type by focusing on code execution rather than direct UI interaction. However, it doesn't explicitly differentiate from all siblings (e.g., browser_console_messages might involve JavaScript output).

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. It doesn't mention prerequisites (e.g., needing a page loaded), exclusions (e.g., when simpler tools suffice), or comparisons to siblings like browser_console_messages for reading JavaScript output. Usage is implied but not explicitly stated.

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