Playwright MCP

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

Annotations already indicate this is a destructive, non-read-only operation with open-world implications. The description adds some context by specifying it evaluates JavaScript on 'page or element', but doesn't elaborate on what 'destructive' means in practice (e.g., could modify page state, trigger side effects) or address rate limits, authentication needs, or specific behavioral traits beyond what annotations provide.

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 extremely concise - a single, clear sentence that communicates the core functionality without any wasted words. It's front-loaded with the essential information and earns its place efficiently.

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?

For a complex, destructive JavaScript evaluation tool with no output schema, the description is minimal. While annotations cover safety aspects, the description doesn't explain what kind of results to expect, error handling, or the relationship between parameters. Given the tool's potential complexity and destructive nature, more context would be helpful despite the good annotations.

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?

With 100% schema description coverage, the schema already documents all three parameters thoroughly. The description adds minimal value beyond the schema - it mentions 'page or element' which relates to the element/ref parameters, but doesn't provide additional syntax examples, constraints, or usage patterns that aren't already in the parameter descriptions.

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 action ('Evaluate') and resource ('JavaScript expression on page or element'), making the purpose immediately understandable. It distinguishes this tool from siblings like browser_click or browser_type by focusing on JavaScript execution rather than direct interaction. However, it doesn't explicitly differentiate from browser_run_code, which might be a similar sibling.

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. With siblings like browser_run_code that might serve similar purposes, there's no indication of when this evaluation approach is preferred, nor any mention of prerequisites or constraints for usage.

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