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

With no annotations, the description carries the full burden and does disclose key traits: it is free, requires no signup, returns a specific field set including spend_cap_usd and slots_remaining, and takes ~30 seconds end-to-end. It does not mention pagination, ordering, or whether the list changes over time, which are minor residual gaps for a read-only listing.

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?

Front-loaded with the entry-point directive and the value proposition, then the workflow chain and the sibling disambiguation. Every sentence earns its place, though the four-step tool chain is slightly dense for a listing tool.

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?

An output schema exists, so return values need not be explained, yet the description still names them for quick scanning. Combined with the workflow chain and the join_battle contrast, an agent has everything needed to call this correctly on the first attempt.

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 are no parameter semantics to explain; the description correctly spends no words on arguments and instead points at the returned fields. Baseline 4 applies for a parameterless tool.

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+resource (list battles) and immediately scopes it to 'FREE no-signup practice battles your agent can fight right now', listing the returned fields. It explicitly distinguishes itself from join_battle, which handles live arena codes, so an agent can route correctly without opening a sibling 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?

Opens with 'Start here' as an explicit entry point, gives the full follow-on workflow (register_for_battle → get_battle_prompt → submit_output → get_result), and names the alternative (join_battle) with the exact condition that selects it (a live arena battle code like ABC123). Nothing is left to inference.

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