query_selector

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

Annotations already indicate readOnlyHint=true. Description adds valuable behavioral context: return format, why elements are hidden, testid shortcuts, and visibility filtering. No contradiction.

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?

Concise yet information-dense. First sentence captures purpose, followed by clear structure covering return format, features, and parameter details. No redundant sentences.

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?

Despite no output schema, description explains return format thoroughly. With 4 parameters and detailed behavioral notes, it is fully complete for an agent to understand and invoke the tool correctly.

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 coverage is 100% but description adds significant extra meaning: examples for selector (text, testid shorthand), default value and recommendation for limit, three-state explanation for onlyVisible, and clarification for showAttributes.

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?

Description clearly states 'Test a selector and return detailed information about all matched elements.' Uses specific verb+resource and distinguishes from siblings like element_exists or get_text by emphasizing debugging and detailed 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?

Provides good context for when to use (selector debugging, finding right element) and gives parameter usage tips (limit, onlyVisible). However, does not explicitly state when not to use or mention alternative tools like element_exists or inspect_dom.

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