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

Annotations already indicate idempotentHint=true and destructiveHint=false, so the description doesn't need to restate those. It adds useful behavioral context: the setting applies globally to all of the player's emails, and blank clears it. It doesn't mention permissions (GM-only) or side effects beyond the attribution, but the core behavior is transparent.

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 description is two sentences, front-loads the main action, and includes the key edge case (blank clears) without any fluff. Every sentence earns its place.

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?

Given the output schema exists and annotations cover idempotency and non-destructiveness, the description is nearly complete. It could mention GM-only permission or that this is a per-campaign setting, but the core behavior and parameter semantics are fully covered. A small gap remains around permissions and scope.

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 already documents all three parameters thoroughly. The description adds the 'applies to all of that player's emails' context and the blank-clears behavior, which complements the displayName parameter description. However, it doesn't add much beyond what the schema already says, so 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 clearly states the action ('Set the name a campaign member's emails are attributed to when collated into a move'), the resource (player/campaign), and the effect (applies to all of that player's emails; blank clears it). It distinguishes itself from siblings like play_create_move or play_update_move by focusing on email attribution display name.

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?

The description explains the context: it applies to all of a player's emails and that passing an empty string clears it back to the player's Embers name. It doesn't explicitly name alternative tools or when not to use it, but the context is clear enough for an agent to select it for setting attribution names.

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