designer-mcp

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes the interactive nature of the tool (user clicks/drags/annotates), cancellation behavior, and output file handling (PNGs in /tmp). However, it doesn't mention potential side effects like browser focus changes or performance considerations.

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 efficiently structured with bullet-like formatting for the three modes, each clearly explaining the user interaction and return values. Every sentence adds essential information about functionality, cancellation, or output handling with zero wasted text.

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?

For a tool with no annotations and no output schema, the description provides comprehensive context about the interactive process, return data structures, and file outputs. The only minor gap is lack of explicit mention about whether this tool requires specific browser state or permissions.

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 has 100% description coverage with clear enum values and descriptions. The description adds significant value by detailing what each mode returns (specific data structures like selector, rect, strokes, etc.) and operational differences between modes, going well beyond the schema's basic mode definitions.

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: 'Activate the picker in the designer browser' with three specific modes (element, area, draw). It distinguishes from siblings like designer_close, designer_open, and designer_screenshot by focusing on interactive element/area selection and annotation rather than basic browser operations or screenshot capture.

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 explicit guidance on when to use each mode: element for clicking one element, area for dragging a marquee, and draw for freeform pen annotation. It also specifies 'Esc cancels in any mode' and mentions using the Read tool to open resulting PNGs, giving clear operational context.

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