set-user-avatar

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

With no annotations provided, the description carries full burden. It discloses mutation (set avatar), default behavior (bridge user), permission requirement (GM-only), and accepted input types. It lacks details on side effects or success indicators, but is otherwise 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 concise: three sentences covering purpose, default behavior, input format, and prerequisite. No redundant information, front-loaded with key action, making it efficient and easy to parse.

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 simple tool with 2 params and no output schema, the description covers purpose, defaults, input types, prerequisite, and permissions. It does not mention what the tool returns on success, but overall it is sufficiently complete for correct invocation.

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 covers both parameters with descriptions (100% coverage), so baseline is 3. The description adds value by clarifying the default for 'user', providing example paths for 'avatar', and referencing upload-asset. This extra context enhances understanding beyond schema.

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 'Set a Foundry user's avatar', specifying the exact verb and resource. It distinguishes this tool from siblings like set-actor-art by focusing on user avatars, and mentions the default behavior for the bridge user, making its purpose unambiguous.

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 explicitly explains when to use (setting user avatar, especially for MCP-Claude), notes the prerequisite of using upload-asset for local files, and states 'GM-only' to indicate access restrictions. This provides clear context for appropriate usage.

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