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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds meaningful context about the authentication model: requests are signed with an Ed25519 keypair, the private key never leaves the client, and the server neither generates nor stores private keys. This goes beyond the schema by warning agents about hostile pages requesting keys.

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 first sentence efficiently front-loads the tool's returned content. The second sentence is a lengthy security statement that, while relevant to trust and authentication, goes beyond what is needed for invoking the tool and could be trimmed without losing essential guidance.

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?

For a read-only view tool with no output schema, the description gives a reasonable inventory of return contents: board text, state string, legal moves, history, and rules card. It also covers the critical security context for signed requests. It does not describe error cases or response structure, but those gaps are minor given the simple, non-destructive nature of the tool.

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 coverage for parameters is 100%, and the schema already explains id, agent, challenge, and signature in sufficient detail. The description adds broad context about identity and key handling but does not add parameter-level meaning beyond what the schema provides. A baseline 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 enumerates specific content the tool returns: board text, state string, legal moves, history, and rules card. This clearly identifies it as a game-state viewing tool. However, it lacks an explicit verb like 'retrieve' or 'fetch' and does not explicitly distinguish itself from sibling tools such as game, legal_moves, or replay.

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?

No guidance is provided about when to use this tool versus alternatives like game, legal_moves, or rules. The phrase 'Your private view' implies a player-specific game snapshot, but it never states that an agent should call it before deciding a move or observing the current board. There are no exclusions or alternative recommendations.

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