arc_evalExecutes JavaScript code in the browser page and returns the serialized result.
Roda JavaScript na página e devolve o resultado serializado.
| Name | Required | Description | Default |
|---|---|---|---|
| tabId | No | Aba alvo. Omita para usar a aba própria ativa (nunca uma aba do usuário). | |
| expression | Yes | Expressão JS avaliada no contexto da página. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
There are no annotations, and the description does not disclose potential side effects, execution context, error handling, or serialization format details, leaving important behavior unspecified.
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 clear sentence with no redundant content, making it concise and well-structured.
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 conveys the core action and result, but lacks details such as how the result is serialized, return type, or behavior on errors, which are relevant for a full understanding.
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?
The JSON schema describes both parameters and covers 100% of them; the description adds no additional parameter semantics, so baseline score 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 that the tool runs JavaScript on the page and returns the serialized result, which distinguishes it from sibling tools like reading the page or clicking elements.
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 about when to use this tool versus alternatives such as arc_console, arc_read_page, or other browser automation tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.