browser_eval

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

With no annotations, the description carries the full behavioral burden. It discloses that this is a powerful escape hatch and returns a value, but says nothing about side effects on page state, execution context, async/promise handling, error behavior, or security implications of arbitrary JS execution.

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?

Two tight sentences with the core behavior front-loaded and the usage caveat second. No wasted text.

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 an arbitrary JavaScript evaluation tool with no annotations, no output schema, and an undocumented parameter, the description is too thin. An agent lacks guidance on execution context, result serialization, and failure modes.

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 the required 'expression' parameter is JavaScript, but provides no details about expression scope, async handling, serialization of return values, or what happens with non-serializable results.

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?

States a specific verb and resource: run JavaScript in the target tab and return the value. It also distinguishes itself from the many specific browser_* siblings by framing itself as a 'powerful escape hatch' and directing callers to prefer specific tools.

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 a clear usage principle: use this only when specific tools do not fit. It does not name which siblings are preferable in which situations, but the general routing guidance is explicit.

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