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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the description's job is to add behavior — and it does: the viewer renders inline in chat, is interactive (orbit plus a settings panel), and stays live and self-updating so repeat calls are unnecessary. This idempotence/auto-refresh detail is real behavioral value not present in the annotations, though permissions or failure modes are not discussed.

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 tight sentences: what it does first, then the trigger conditions, then the anti-trigger with its reason. No filler, nothing buried, and the most important constraint is front-loaded.

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 one-parameter, no-output-schema tool whose result is a UI surface rather than data, the description covers everything an agent needs: what appears, where it appears, that it is interactive, and when to invoke or skip it.

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% and the single forgeId parameter is already documented with its accepted forms and the source tools that return it. The description adds no parameter-level syntax or format information beyond that, so the baseline 3 applies.

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 (Show) and resource (a forge) plus the delivery surface (PartForge's live 3D viewer, inline in chat) and what the user can do with it (orbit, try settings). An agent understands the action immediately. It does not, however, name or distinguish itself from nearby siblings such as viewer_load_forge or viewer_forge_status, which is the only thing keeping this from a 5.

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 explicit when-to-use conditions (after a forge's first successful build; whenever the user asks to see the forge) and an explicit when-NOT-to (don't call after every edit, because an open viewer self-updates). That is strong, actionable routing guidance. It stops short of a 5 only because it never names an alternative tool for the cases it excludes.

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