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

With no annotations, the description carries the full burden, and it does disclose one genuinely useful behavioral trait: legal moves are included only on your turn, so the response shape varies by state. It says nothing about read-only semantics, authentication requirements (the api_key param exists but the behavior around it is unstated), or what happens for a missing/invalid game_id.

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?

A single well-packed sentence that front-loads the most important output (position/FEN/board) before secondary details. Every listed item is informative; the only weakness is the em-dash clause that drifts into state-conditional behavior mid-sentence.

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?

Because there is no output schema, the description must describe the return payload, and it does so thoroughly — arguably the strongest part of this definition. Gaps remain around game_id provenance and error/failure behavior, but for a simple read tool with two parameters the coverage is close to sufficient.

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 only 50% — api_key is documented in the schema, but game_id has no description at all. The description does not compensate: it never explains game_id's format, where to obtain it, or whether it must be a game you are seated in. The two-parameter schema is left half-explained.

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 enumerates exactly what a caller gets back: FEN, ASCII board, move list with reasons, side to move, clock, and legal moves. That makes the resource unambiguous (a single game's state), even though the sentence is a noun phrase rather than a verb+object and never disambiguates against siblings like chess_review, chess_my_games, or chess_play.

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?

There is no guidance on when to call this versus chess_my_games (listing games) or chess_review (post-game analysis), and no stated prerequisites such as needing to be a participant in the game. The only usage hint is implicit: legal moves are returned 'if it is your turn', which hints at a pre-move inspection use case but is not framed as guidance.

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