Emulate page conditions

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

Beyond the annotations (idempotentHint=true, destructiveHint=false), the description discloses important behavioral traits: persistence across navigations, the independent-parameter behavior, and the concrete side effect that enabling `touch` changes `click` behavior (falls back to scripted path with isTrusted=false). It also warns about UA client hints not being touched by the user_agent parameter. This adds meaningful context beyond what annotations provide.

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 appropriately sized: four sentences, each serving a distinct purpose—listing capabilities, stating scope and parameter usage, mentioning the alternative tool, and warning about a behavioral interaction. No redundant or vague phrasing; the most important 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?

With 6 fully schema-described parameters, an output schema present, and annotations covering mutability and idempotence, the description still adds crucial context: persistence, how to reset via reset_emulation, the explicit alternative emulate_device, and the touch-click caveat. This is sufficient for an agent to select and safely invoke the tool without additional external knowledge.

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%, so the baseline is 3. The description adds extra meaning by explaining that 'Every parameter is independent — pass only what you want to change, leave the rest at their defaults,' which clarifies the default-value semantics beyond the schema. It also highlights the interaction between the viewport's `touch` flag and click behavior, which is not evident from the schema alone. These additions justify a 4, though the schema already provides thorough descriptions for each parameter.

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 opens with a specific verb and the list of emulatable resources: 'Emulate network, CPU, geolocation, user agent, color scheme or viewport.' It clearly distinguishes from the sibling tool emulate_device by explicitly naming it as the alternative for real phone/tablet emulation, and also mentions reset_emulation for clearing the state.

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 gives explicit when-to-use guidance: 'To emulate a real phone or tablet, use emulate_device instead' and explains why (coherent set of user agent, client hints, viewport, DPR, touch). It also states the scope ('Applies to the selected page and persists across navigations until reset_emulation') and how to use parameters independently with defaults.

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