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

With no annotations, the description carries the full burden, and it discloses key behavioral traits: this opens an interactive hosted app rather than returning data, output differs by argument, and it can also be launched from the ChatGPT/Codex sidebar. It does not cover auth/permission requirements or failure behavior, though the token parameter description partially addresses session-token handling.

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, front-loaded with the core purpose and the two modes; every sentence adds routing or parameter value. The trailing sidebar note is a mild fragment but still relevant context.

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 2-param app-launcher with a fully-described schema and an output schema present, the description covers purpose, both argument modes, sibling alternatives, and launch surfaces. Return-value explanation is rightly omitted given the output schema; only failure/permission behavior is unaddressed.

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 baseline is 3, but the description adds meaning the schema does not: omitting projectId changes the tool into a full-catalog listing with preview counts only, and projectId is sourced from catalog_list_projects. This clarifies the conditional semantics of the optional parameter.

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 (Open) and resource (hosted preview catalog browser app), then immediately clarifies its two modes: no-arg catalog listing vs. projectId-scoped preview listing. An agent can distinguish it from catalog_list_projects, catalog_list_previews, and ui_builder_open without opening any schema.

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?

Explicitly states when to use each mode ('With no arguments it lists every catalog...; pass projectId to list one catalog's previews') and names the non-app alternative path (catalog_list_projects then catalog_list_previews with a catalog id). Routing guidance is complete.

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