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

With annotations present the bar is lower, and the description still adds real value: 'The server opens neither' and 'it records that you asked for this world' explain why readOnlyHint=false and idempotentHint=false despite the tool appearing to just resolve URLs. This reconciles the non-read-only, non-idempotent profile with observable behavior rather than contradicting it.

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 core deliverable (the two URLs plus `next`) is front-loaded, and the exclusion of world.open follows. Some clauses are dense and a touch circuitous, but there is little outright waste.

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?

No output schema exists, and the description compensates by naming the returned pieces (browser URL, zero:// URL, next sentence). Combined with the annotations covering the open-world side effect, an agent has enough to call it correctly; only the exact response shape remains unstated.

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 schema already documents guid, name, and the world alias. The description's 'Pass `name` (looked up via world.list) or `guid` (already-resolved)' largely restates the schema's own text. Baseline 3 is appropriate since the structured field does the heavy lifting.

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 states a specific resource and outcome - it returns the browser URL and `zero://` URL where a world opens, plus a `next` field naming the opener. It explicitly distinguishes itself from world.open, so an agent can tell what it does apart from siblings. The framing 'Answer where a world opens' is slightly indirect but the substance is clear.

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?

It gives an explicit routing rule: use world.open when you intend to edit, because that tool also checks edit access and the branch. This names the alternative and the selecting condition. It stops short of stating the affirmative 'use this when you only need to know where it opens,' leaving one small inference.

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