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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful non-obvious context: opening the app does not generate media or spend credits, which is exactly the cost concern an agent would have before calling an app-opening tool. It doesn't say what the opened app renders or whether prior session state matters, so it's not a 5.

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 short sentences, front-loaded with the action, then the capabilities, then the cost caveat. Every sentence carries information an agent would otherwise have to guess, and nothing is repeated from the annotations verbatim.

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 zero-parameter, fully annotated tool with an output schema, the description covers purpose, contents and cost behavior. The only remaining ambiguity is what the caller experiences after invocation (UI surface, whether it targets an existing project), which is minor given the output schema presumably conveys the result.

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 tool takes zero parameters, so there is no parameter meaning for the description to add; baseline 4 applies. The description doesn't need to compensate for any schema gaps since the schema is empty and fully covered.

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?

"Open the complete VideoGen app inside ChatGPT" gives a specific verb (open) and resource (the VideoGen app), which is distinct from the many generate_*/create_* siblings. The follow-up sentence listing navigation, assistants, examples, library and editor further pins down what is being opened. It stops short of naming a sibling outright, so it's clear but not maximally differentiating (open_home vs. get_app_deep_link / open_uploader is left implicit).

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 tells the agent what becomes available after opening (navigation, assistants, editable examples, media library, editor), which implies the use case is entering the interactive UI. However, it never states when to prefer this over alternatives such as get_app_deep_link or open_uploader, nor are there any exclusions or prerequisites. Usage is inferable but not guided.

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