session_screenshot

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

With no annotations, the description carries the burden of behavioral disclosure. It usefully states the capture scope ('visible tab area') and the response format ('base64 PNG or JPEG'), which are important behavioral facts. However, it does not mention failure behavior, default format, or whether the operation has any side effects, leaving gaps for an agent to discover.

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, front-loaded sentence with no filler. Every word contributes: the action, the scope, and the output format are all stated efficiently. It is appropriately sized for the information it provides.

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 tool has four optional parameters, no output schema, and no annotations, yet the description only covers the basic action and return format. It does not explain the effect of windowId, how format and quality interact, or what the default behavior is. An agent calling this tool correctly would need to rely on external knowledge or make assumptions.

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 description adds no parameter-level meaning. Two of the four parameters lack schema descriptions (format, windowId), and the description does not clarify their semantics, defaults, or whether quality only applies to JPEG. Since schema coverage is only 50% and the description does not compensate, the agent has limited guidance for constructing valid calls.

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 verb ('Take a screenshot'), the resource ('visible tab area'), and the output format ('Returns base64 PNG or JPEG'). It is specific and self-contained, and among the sibling tools it is the only one that explicitly captures a screenshot, so there is no ambiguity about its purpose.

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 implies the use case is visual capture of the visible tab, but it does not explicitly state when to use this tool versus alternatives like session_snapshot or session_read_page. No exclusions or conditions are provided, so an agent must infer when a screenshot is the right choice.

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