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

Annotations declare destructiveHint=true and readOnlyHint=false, and the description adds consistent value: it discloses that the operation is a signed move requiring 'resign: true', and it layers on the Ed25519 identity model ('your identity is your Ed25519 keypair... the server never generates or stores private keys') so an agent knows no key-entry flow is ever legitimate. This is additional behavioral context beyond the annotations, not a contradiction.

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 is tight and front-loaded, but the second sentence is a long, system-wide security statement that reads as platform boilerplate, and the '(signed)' tag is redundant with the following explanation. Overall compact at two sentences, but it carries some generic filler.

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?

The rich schema plus destructive/readOnly annotations cover much of the operational surface, and no output schema obligates return-value documentation. However, the description stops at the act of resigning and never discloses the consequence (the game ends, resignation is irreversible, the opponent wins), which an agent deciding to invoke a destructive signed action would want to know.

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 100%, so the schema fully documents id, body, agent, challenge, and signature, including the exact signing strings. The description's only parameter-level addition is restating 'must include resign: true', which the body schema already states, so the baseline of 3 applies.

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 opening verb 'Resign' names a specific action and resource ('the game'), and the parenthetical 'a signed move with resign: true' captures the mechanism. The purpose is unambiguous on its own, though it does not explicitly contrast with the sibling 'move' tool, which shares the same signed-move mechanics.

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 given on when to use this tool versus 'move' or 'offer_draw', the closest siblings. The only usage signal is the self-evident verb 'Resign', and the description never states exclusions or conditions such as resigning being irreversible or ending the game.

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