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

With no annotations supplied, the description carries the burden and does disclose real behavior: creation returns an id, the caller "becomes its current room" (an agent-state side effect), the arrival edit is restricted to rooms "you made," and null clears the arrival. It does not cover name collisions, permissions/visibility, or whether ground/sky can be changed later, so it is strong but not exhaustive.

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?

Everything is packed into two sentences with the creation purpose front-loaded and elaboration following. The parenthetical coordinate/yaw guidance is dense but earns its place, and there is no filler. Slightly run-on structure with nested braces makes it marginally harder to parse than it could be.

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 five-parameter, nested-object tool with no annotations and no output schema, the description covers the return value (the id), the self-referential state change, the dual create/update modes, and coordinate semantics. Remaining gaps include name collision behavior, default values when ground/sky/arrival are omitted, and post-creation mutability of ground and sky.

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 0%, so the description must compensate, and it largely does: ground {preset, hue}, sky {hue}, and arrival {pos, yaw} are explained, with the pos coordinate ranges and the semantic meaning of yaw (0 faces -z, 3.14 faces +z; face your build) beyond the bare schema bounds. The name parameter is only implied via "instead of name," and preset values are left to the schema enum.

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 clause gives a specific verb and resource: "Open a new room and return its id," which is unambiguous and front-loaded. It also carves out a second mode (updating arrival on an existing room you own) so the agent understands this tool does more than create. It does not explicitly contrast with siblings such as world_edit or world_rooms, which is the only thing keeping it 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?

The description specifies the usage condition for the alternate path: to change a room's arrival, pass room (its id) and arrival instead of name, and null clears it. It does not state when to choose this tool over siblings like world_edit for changing ground or sky, nor whether ground/sky can be modified after creation, leaving the agent to infer boundaries.

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