Evaluate JavaScript

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

Annotations already indicate destructiveHint=true and openWorldHint=true, so the description's claim of 'evaluate' is neutral and does not contradict. However, the description adds no extra behavioral context, such as the potential for side effects or security implications, which would be valuable given the destructive annotation.

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 sentence of six words, making it extremely concise. It is front-loaded with the key action. However, the brevity is at the cost of completeness, so while structurally efficient, it sacrifices necessary detail.

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?

Given the tool has five parameters, no output schema, and annotations indicating destructive and open-world behavior, the description is far too sparse. It does not explain the return value, how to use the parameters, or the execution context, leaving significant gaps for an agent to use the tool correctly.

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 only mentions 'expression' and 'page or element', which loosely maps to the 'function' and 'target'/'element' parameters, but fails to explain the meaning of '_meta', 'filename', or the distinction between 'target' and 'element'. This is insufficient for the five parameters.

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 action ('Evaluate JavaScript expression') and the context ('on page or element'), which is specific and uses a verb-resource structure. However, it does not differentiate from the sibling tool 'browser_run_code_unsafe', which has a similar purpose, missing an opportunity to distinguish.

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?

No guidance is provided on when to use this tool versus alternatives, such as 'browser_run_code_unsafe' or other browser interaction tools. There is no mention of prerequisites, limitations, or when not to use it, leaving the agent without context for selection.

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