js

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

With no annotations, the description takes full responsibility for disclosing behavior. It explains evaluation semantics (bare expression vs. script), automatic function wrapping for 'return', how non-serializable values are handled (Infinity/NaN/-0/BigInt), and error behavior (returns ok:false rather than faking success).

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?

Every sentence contributes value, covering usage, edge cases, and error handling in a compact format. The description is front-loaded with the primary purpose and immediately provides an illustrative example.

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 JS execution tool, the description covers the core semantics, error handling, and non-standard values. It could gently mention the structure of the successful return value (e.g., ok:true), but given the lack of an output schema, the current detail is largely sufficient.

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?

Although schema coverage is 0%, the description thoroughly clarifies both parameters: 'code' contains the JavaScript expression/script, and 'tab' defaults to the active tab. It adds significant meaning beyond the raw schema.

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 tool executes JS in the page and returns the completion value, with a concrete example ('document.title'). It is easily distinguishable from sibling tools like click or navigate, which have different purposes.

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?

Usage context is implied through examples (e.g., bare expression vs. script, tab defaulting to active tab), but there is no explicit guidance on when to choose this over alternatives like cdp or exec_python. The description implies usage but does not provide exclusions or mention alternatives.

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