browser_eval

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

With no annotations, the description carries full disclosure burden. It transparently notes that the tool can read DOM, storage, and send requests, which hints at side effects. However, it does not explicitly state that evaluation can modify page state or cause side effects beyond those mentioned.

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 a single, well-structured sentence with examples and a key caveat. Every phrase adds value, no wasted words, and critical information is front-loaded.

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?

The description explains what the tool does and its capabilities, but lacks details on the return format (type, serialization) and error handling. Given no output schema, this omission reduces completeness for an arbitrary-JS-execution tool.

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% with a brief parameter description. The tool description adds meaningful context: examples of valid expressions, warning against arrow functions, and scope (read DOM/storage/requests), which goes beyond the schema's 'JS expression/statement'.

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 that the tool executes JS expressions on the page and returns the result, with specific examples (e.g., document.title, 1+1). It distinguishes from arrow functions and lists capabilities (read DOM/storage/send requests), differentiating it from sibling tools like browser_click or browser_navigate.

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 implicitly indicates use for evaluating JS, but lacks explicit guidance on when to use this tool versus alternatives (e.g., browser_snapshot for page state). It warns against arrow functions but does not specify when not to use it or provide context for preferred scenarios.

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