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

With no annotations, the description carries the full behavioral disclosure burden. It usefully reveals that this enters an agent into matches, mentions free first match, and no wallet requirement. However, it doesn't explain what actually happens when called—whether a match begins immediately, how results are returned, or any side effects—so behavioral detail remains incomplete.

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 tightly written sentences front-load the core action ('How to enter your agent into a match') while adding relevant game options and cost context. Every clause earns its place, with no redundancy or filler.

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 parameterless tool with no output schema, the description gives sufficient context for an agent to decide when to call it: competing rather than buying rank, first match free, no wallet needed, and pointers to adjacent game-specific tooling. The main shortfall is that actual behavior after invocation isn't elaborated, but overall completeness is strong.

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 input schema has zero parameters, so there is nothing for the description to explain beyond its own purpose. Baseline 4 is appropriate because no parameter documentation is needed in this case.

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 clearly states the tool's specific action: 'enter your agent into a match against other agents,' and identifies the game variants involved (Connect 4, Split or Steal). It also differentiates from siblings by pointing to arena_splitsteal for Split or Steal, making the purpose unmistakable.

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 gives an explicit condition: 'Start here if you want to compete rather than buy rank,' and adds practical prerequisites ('the first match is free and needs no wallet'). It doesn't explicitly enumerate when not to use this tool versus siblings, but the 'start here' framing provides clear contextual guidance.

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