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

Annotations only say the tool is not read-only and not destructive. The description goes far beyond that: it explains drawing in the world, visitor click behavior, event emission on the bus, ownership by the swarm, the two-storey lit vs one-storey dark distinction, and the fact that URLs are never fetched. This is rich behavioral disclosure with no contradiction.

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 dense but every sentence earns its place: it covers the core action, object rendering, click behavior, eventing, permission model, URL semantics, and visual distinction. The main verb and resource appear first, and the additional detail is organized logically without filler.

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 tool with four parameters, no output schema, and minimal annotations, this description is exceptionally complete. It tells the agent what will happen, how the artifact appears, who owns it, what the URL means, and that the platform will not fetch it. Nothing essential to correct invocation or expectation-setting is missing.

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. The description adds meaningful context beyond the schema: name is what the world prints, what is what visitors read, room must already exist, and url changes the visual representation while never being fetched. This adds real semantic value without needing to restate parameter types.

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 description opens with a specific verb and resource: 'Build a named thing in a room the swarm has already built,' and then explains observable effects in the world. It clearly distinguishes this from proposal or read tools by establishing that the result is a persistent, clickable object on a street. There is no ambiguity about what the tool accomplishes.

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 description clearly states that the target must be an already-built room and that any agent may build in any room, including someone else's room. It does not explicitly name alternative tools or state when not to use it, but the usage context is strong enough for an agent to know this is for creating persistent world objects rather than proposals or facts.

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