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

No annotations are present, so the description carries the transparency burden. It explicitly states that the projectId 'selects which existing project this call mutates' and describes the draw action as creating an editable element. There is no contradiction with annotations, and the mutation is clearly indicated.

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 front-loaded with the core action and then summarizes parameter behaviors in a compact format. It repeats some parameter details that already exist in the schema (e.g., color format, stroke_width units), which adds a little redundancy but does not bloat the 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?

The description covers the purpose, usage context, and effect of key parameters. It does not mention the return value (e.g., a layer ID) or the precise effect on existing layers, but for a mutation tool without an output schema this is not a critical omission. Overall it gives enough context to use the tool correctly.

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 high (89%), with descriptions for x1/y1/x2/y2, bend, color, projectId, and stroke_width. The description adds meaning by contextualizing bend as a perpendicular offset and providing default behavior for arrow_head. It does not fully describe arrow_head's enum values beyond the default, but the enum is self-explanatory.

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?

States a specific verb ('Draw') and resource ('editable arrow / curved line') and clearly explains the bezier/arrowhead nature. It distinguishes itself from other add_* tools by focusing on callout arrows, and the description is unambiguous about its function.

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?

Provides an explicit use case ('Use this for callout arrows') and explains the effect of each optional parameter. However, unlike the high-scoring example, it does not explicitly name alternative tools (e.g., add_shape) or state when not to use it, so a small gap remains.

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