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

Annotations already signal readOnly=false and destructive=false; the description adds the auth prerequisite for daily mode and the resume-instead-of-restart behavior, which are not visible in the schema. It does not elaborate on openWorldHint or what happens if a game is already active, but it goes beyond what annotations alone provide.

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?

Two sentences with no filler: the first states the core action and variants, the second adds the key daily-mode constraint. Every sentence earns its place.

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?

The mode logic is well covered, but there is no output schema and the description does not say what a successful start returns or what happens when a game is already in progress. Given the tool's state-changing nature, these are meaningful omissions.

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?

With 0% schema description coverage, the description must carry parameter meaning. It explains the role of mode and accountToken, but is silent on the name parameter and on how game selection interacts with modes, so the compensation is only partial.

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 uses a specific verb ('Start') and resource ('game play'), then clearly distinguishes guest free play from authenticated free/daily play. The action is distinct from siblings like arcade_make_move and arcade_read_game.

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 states a concrete rule: daily mode requires an account token and resumes the account's current UTC-day attempt, so an agent knows when to choose daily over free. It does not explicitly list when to avoid this tool in favor of a sibling, so it stops short of a 5.

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