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

Annotations already declare this a safe read-only, idempotent, non-destructive operation, and the description adds real behavioral context the annotations don't cover: the output is an interactive in-chat viewer with per-part click text, and the requirement to simulate first. It stops short of saying what happens when the design is invalid or how the viewer behaves on re-invocation, so not a full 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 sentences, front-loaded with what the user sees, then input sourcing, then the prerequisite and the exclusion. Every clause carries distinct information with no restatement of the name or title.

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 complex nested-input tool with no output schema, the description covers purpose, interaction model, input sourcing, and the simulate-first dependency, which is enough to call it correctly. Minor gaps remain around failure modes for an invalid design and whether the viewer is persistent.

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 3 is the floor, and the description earns above that by clarifying the exclusive-or relationship between the two optional parameters and by sourcing example ids from list_examples, neither of which the schema states. It doesn't add anything about the nested design fields, which the schema already documents in depth.

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?

A specific verb ('show') plus resource ('a design ... in an interactive 3D viewer in the chat'), with the rendering behavior spelled out (buttons, levers, tick-by-tick, orbit, click-to-explain). It explicitly names the sibling it is not ('Do not use it to test a design: use simulate'), so an agent can separate it from simulate without reading schemas.

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?

Gives the two input paths ('Give either design, or example'), where example ids come from (list_examples), a precondition ('Simulate the design first'), and an explicit exclusion routed to an alternative tool. Nothing about when-to-use is left to inference.

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