browser_inject_css

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

There are no annotations provided, so the description bears full responsibility for behavioral transparency. It states 'inject custom CSS' but does not disclose the effect scope (e.g., whether it persists across navigations, replaces existing styles, or is reversible). No details about side effects or limitations are given.

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, concise sentence that immediately conveys the action and target. Every word is meaningful and there is no redundant fluff. It is appropriately front-loaded for quick agent reading.

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 simplicity of the tool (one parameter, no output schema, no annotations), the description is minimally sufficient but lacks important context about the behavior of the injected CSS. It does not mention whether the styling persists, how it interacts with existing CSS, or if it affects the current page only. For a browser automation tool, this additional context would aid correct invocation.

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 schema provides 100% coverage for the single parameter 'css' with description 'CSS to inject'. The tool description repeats this concept but adds no new meaning. Since the schema already documents the parameter adequately, the baseline of 3 is appropriate, though the description does not enhance understanding beyond the 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's purpose: 'Inject custom CSS into the page' with a specific verb (inject) and resource (custom CSS). It is distinct from most sibling tools like browser_navigate or browser_click, but does not explicitly differentiate itself from browser_execute_js, which could also inject CSS via JavaScript. Thus it is clear but lacks sibling differentiation.

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 provides no guidance on when to use this tool versus alternatives. It does not mention that browser_execute_js could be used for the same purpose, nor does it explain any prerequisites or scenarios where this tool is preferred. Usage is only implied by the tool name and description.

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