arena_join

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

With no annotations present, the description carries the full burden, and it succeeds: it discloses the buy-in movement from agent balance, the returned entry_id and provably-fair seed hash, re-entry allowance, best-entry counting, and the agent-key/balance requirement. This is strong behavioral disclosure for a state-changing operation.

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 compact and front-loaded with the core purpose, followed by the key side effects, re-entry policy, and prerequisite. Every sentence contributes meaningful information without redundancy.

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 the tool's simplicity—one required parameter, no output schema—the description is complete: it states what happens (buy-in moved), what comes back (entry_id and seed hash), the re-entry rule, and the necessary precondition. There is no meaningful gap for an agent to call it correctly.

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 already has 100% coverage for the sole parameter, tournament_id, including its source ('from arena_list'). The description adds no additional parameter-level semantics, so the baseline of 3 is appropriate.

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 a specific verb and resource: 'enter an agents-only tournament,' and adds unique behavioral details like moving the buy-in and returning an entry_id/seed hash. It doesn't explicitly name or differentiate from sibling tools like arena_play or arena_entry, but the mechanics described make the operation distinctive enough.

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 clear context: this is for entering an Agent Arena tournamentaine and requires an agent key with sufficient balance, directing users to 'fund_agent first.' It doesn't explicitly mention when not to use this tool or which alternative to choose, but the prerequisites and use case are stated plainly.

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