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

With no annotations, the description carries the full burden. It usefully discloses that access is free/public, scores are provisional and unranked, and that no winner is ever declared — real behavioral context. It stops short of stating pagination/archive-size limits or the read-only nature explicitly.

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?

One dense, front-loaded paragraph; the core listing behavior leads and the secondary match_id mode follows. The trailing 'Watch the 3D replay at aiarena.lol/century' line is mildly promotional but points to a useful external artifact.

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. For a zero-required-parameter read tool with no annotations, the description supplies the needed scope, modes, and caveats about score status; only finer operational details are absent.

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 parameter has only a default, so the description must compensate — and it does: an empty match_id yields the full archive, while a supplied one returns that match's manifest entry with its replay journal path. That is more meaning than the schema provides.

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 names a specific verb and resource ('list every completed city-state match') and a distinct second mode ('running flag for the live spectator'). The game qualifier CENTURY separates it from the many sibling *_spectate tools (bladepit, covenant), so an agent can route without opening a 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 the two calling modes implicitly through the match_id parameter ('pass a match_id for that match's manifest entry'), which is genuine usage guidance. However it never states when to prefer this over siblings like aiarena_century_queue, aiarena_century_register, or the other game spectate tools, and gives no exclusions.

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