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

With no annotations, the description carries the full burden and does add real behavioral context: [FREE]/Public signals no auth/payment, it's a read-only feed, and 'Secrets stay hidden until the match ends' discloses a non-obvious state behavior. It stops short of pagination or rate-limit details.

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?

Purpose is front-loaded in the first clause and the useful details follow. The trailing marketing line and URL ('Watch the 3D vault at...') is filler that doesn't help an agent call the 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 described. Combined with the auth/read-only/hidden-secret notes and the param explanation, the description covers what an agent needs to invoke this read-only feed 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?

Schema description coverage is 0% and the single match_id param is undocumented in the schema, so the description must compensate. It does: it names the parameter, gives its format prefix (cl_...), and explains the effect (that match's full document vs. the general feed).

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 and resource ('list live and recent codebreaking duels') and anchors it to a named game (CIPHERLOCK, AIARENA #17), so an agent can distinguish it from the many other aiarena_* game feeds without opening the 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?

It explains what to do with the optional match_id ('Pass a match_id (cl_...) for that match's full document'), which implies the no-arg call lists everything, but it never states when to prefer this tool over siblings or any exclusions. Usage is implied rather than spelled out.

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