query_selector

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

No annotations are provided, so the description must carry the full burden. It declares the tool is for querying (implying read-only) and lists return fields, but does not explicitly state side effects, error conditions (e.g., element not found), or permission requirements. The behavioral disclosure is adequate but not comprehensive.

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 sentences with no wasted words. It front-loads the purpose and then lists return values. Each sentence earns its place.

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 query tool with 3 parameters and no output schema, the description covers the basic functionality. However, it lacks details on error handling (e.g., missing element), return structure (no schema), and any dependencies or prerequisites. It is minimally complete but leaves gaps.

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% (all parameters have descriptions). The description only adds context that the selector is a CSS selector, which is already in the schema. It does not explain the meaning of sessionId or pageId beyond what the schema provides. Baseline 3 is appropriate.

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 'Query', the resource 'single element by CSS selector in a renderer page', and the return values ('tag name, text, attributes and bounding rect'). This distinguishes it well from sibling tools like get_dom_snapshot (full DOM) and evaluate_in_renderer (JS execution).

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 implies usage for querying a single element but provides no explicit guidance on when to use this tool vs alternatives (e.g., get_dom_snapshot for full DOM, evaluate_in_renderer for JavaScript). No when-not-to-use information is given.

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