browser_screenshot_tab

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

With no annotations provided, the description carries full behavioral disclosure burden. It successfully communicates the tool is disabled, the auto-focus side effect, and the return format ('base64 string without the data URI prefix'). It does not disclose error conditions (e.g., tab not found) or performance constraints (image size limits), preventing a 5.

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?

Three components in optimal order: status flag '[Disabled]' front-loaded for immediate visibility, action statement ('Capture a screenshot...'), and return value specification ('Returns the image...'). Zero redundancy; every clause provides unique information not found in structured fields.

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?

Despite lacking an output schema, the description adequately specifies the return value format. It covers the essential behavioral context (disabled status, auto-focus) for a single-parameter screenshot tool. A 5 would require additional context such as error handling for closed tabs or image dimension constraints.

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 100% (tabId is fully documented in the schema as 'Tab ID to screenshot — the tab will be focused automatically before capture'). The description mentions the auto-focus behavior but does not add semantic meaning beyond what the schema already provides, warranting the baseline score of 3.

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 explicitly states the tool captures 'a screenshot of the visible area of a browser tab as a base64-encoded PNG image'—specific verb, resource, and output format. The '[Disabled]' prefix immediately signals operational status. It clearly distinguishes from siblings like browser_get_tab_content (HTML/text) or browser_focus_tab (mere focus).

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 '[Disabled]' status provides critical usage guidance (do not invoke). It discloses the auto-focus side effect ('tab is automatically focused before capture'), which helps agents understand they need not call browser_focus_tab first. However, it lacks explicit guidance on when to use this versus browser_get_tab_content or error handling for invalid tabIds.

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