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

With no annotations, the description carries the full burden of behavioral disclosure. It says 'Takes no arguments' — but the schema shows an optional token parameter. It does not state whether this is a read-only operation, whether it opens a UI window, what side effects occur, or what the output schema contains. The mention of sidebar and deep link is contextual but does not inform behavior.

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 two sentences and front-loads the main action. It is concise and well-structured, though the second sentence mixes invocation channels with functionality in a way that is slightly scattered. No wasted words.

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?

Given there is an output schema, the description need not explain return values. However, with no annotations and a mutation-ambiguous action ('Open'), the description should clarify whether this is a read-only UI action, whether it requires permissions, and how it relates to the token parameter. The claim 'Takes no arguments' is misleading given the schema, leaving the agent under-informed about a tool that may have side effects.

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?

The schema has 100% description coverage for the single 'token' parameter, which is thoroughly documented in the schema itself. The description adds no information about the token — the only parameter — and actually contradicts the schema by claiming 'Takes no arguments.' Baseline 3 would be appropriate if the description were silent, but the explicit false statement slightly reduces value.

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 'Open the UI Builder's design list' — a clear verb and resource — but then muddies the purpose with 'pick a design to see it as the editor draws it,' which is actually a description of viewing, not opening. It does not clearly distinguish this tool from siblings like ui_builder_list_designs or ui_builder_view. The core action is discernible but not sharply defined.

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 says 'Also opens from the ChatGPT/Codex sidebar, and a deep link to /design/<id> opens one design,' which describes alternative invocation paths, not when an AI agent should call this tool versus alternatives. There is no guidance on when to use ui_builder_open vs ui_builder_list_designs, ui_builder_view, or ui_builder_get_design. Usage context is implied but not explicit.

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