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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral context on top: the exact payload assembled into the prompt and the includeDesign=false escape hatch for teams with their own design system. It stops short of saying how large the prompt can get or whether screens are truncated.

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?

Two sentences, with the artifact contents front-loaded and the accepted id forms trailing, which matches how an agent reads. The content list is long but each item earns its place by defining the output. Only minor trimming is possible.

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 no output schema, the description correctly carries the burden of describing the return payload, and it does so concretely. Combined with annotations covering the safety profile and a fully documented 5-parameter schema, an agent has nearly everything needed; only edge cases like large reference sets or truncation go unmentioned.

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, but the description adds the referenceId naming grammar ({product}-onboarding, {product}-collection, single screen id) that goes beyond the schema's flat example list, clarifying the accepted id families. Other parameters (goal, stack, screens, includeDesign) are only covered by the schema.

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?

Names a specific verb and artifact (build a handoff prompt) and enumerates exactly what the artifact contains: ordered screens with notes, observed transitions, image URLs, design guide, checklist. That composite output is distinctly different from what siblings like get_design or get_screen return, so an agent can route correctly without opening any schema.

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 second sentence tells the agent what to pass as referenceId (an onboarding flow, a whole collection, or a single screen id), which is really input guidance. It never says when to choose build_handoff over check_my_ui, get_design, or get_product, nor when not to use it. Usage is implied by the described output rather than stated.

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