generate_pen_cup

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

With no annotations, the description must carry the full behavioral burden. It does disclose real traits — free tier capped at 3 pen cups/month, Pro unlimited, QR decoration requires Kiln Business, oversized meshes decimated for the stage, and a viewer panel opening on success. However it never says whether a persisted design is created, whether sign-in is required for the base call, or what the tool actually returns, so key mutating behavior stays opaque.

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 first sentence is well front-loaded, but the body then repeats the inline-3D-stage point twice (opening sentence and a dedicated all-caps section), injects a marketing URL and upgrade link, and detours into a confusing "MAKE DOORS" tangent about design_session. Substance is diluted well below what a 16-param generator description should carry.

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 parameter-rich, annotation-free, output-schema-free generator the description covers quota, tier gating, and preview/stage behavior, which is useful. But it omits the essentials an agent needs to call correctly — whether a design artifact is persisted, whether the call is idempotent or costly beyond quota, and what the PNG/stage output represents — leaving it only partly complete.

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% but each parameter is documented only as a terse "Default: X" string, and the description adds nothing about shape/bottom/material options, units, or how brief_id and color_overrides interact. Per the high-coverage baseline, 3 is the appropriate floor — the schema technically documents all 16 params, but no semantic depth is layered on top.

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 opening sentence gives a specific verb and resource ("Generate a desktop pen / brush cup with optional decoration") plus a secondary capability (QR code, gated to Business tier). It does not differentiate from other product generators in the sibling list (generate_coaster, generate_pet_bowl, generate_decorated_product), so an agent must infer the boundary from the object name alone.

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 "MAKE DOORS" block hints at a workflow (design_session absent, compile_scad as the make→preview→iterate loop), but it is framed as meta-commentary about the installation rather than guidance on when to call this tool versus a sibling product generator. No exclusions or prerequisite conditions are stated for choosing generate_pen_cup over generate_decorated_product or generate_coaster, leaving usage only implied.

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