Try a CSS/Playwright selector

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

Annotations already mark the tool as read-only, so no contradiction exists. The description adds useful behavioral context beyond annotations by specifying the operation is scoped to the current tab and by disclosing which element properties are inspected. It does not describe error behavior or match limits, but the read-only annotation lowers the burden.

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 two tight sentences. The first front-loads the action, scope, and output fields; the second gives a concrete repair use case. There is no filler or repetition of schema/annotation information.

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 simple read-only debugging tool with just two parameters and no output schema, the description covers what it does, what it returns, and when to use it. It could mention whether it waits for elements or what happens on zero matches, but those are minor gaps given the tool's debugging purpose.

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 0%, so the description must compensate. It clarifies that 'selector' is a CSS/Playwright selector used to find matching elements on the current tab. The 'limit' parameter is not explained in the description, though its name, default, minimum, and maximum in the schema make its meaning reasonably inferable.

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 states a specific verb-resource pair: 'Count and describe elements matching a selector on the current tab' and enumerates the exact fields returned. The title 'Try a CSS/Playwright selector' further clarifies the selector type, making it clearly distinct from siblings like debug_click and debug_page_text.

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 an explicit use case: 'Use to repair src/linkedin/selectors.ts when LinkedIn changes markup.' This tells the agent when the tool is appropriate. It does not explicitly name alternative tools or exclusions, but the targeted repair scenario is strong contextual guidance.

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