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

Annotations already declare readOnlyHint, destructiveHint false, and openWorldHint false. The description adds useful context that this returns only a schema, not per-user data, and scopes the output to one specific model field. Yet the phrase 'Use this to declare new player-specific stats' is ambiguous for a read-only getter and could mislead an agent about whether this tool performs writes.

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 front-loaded with the core action and scope. It runs to four sentences but each adds information (what it returns, what it does not return, and a usage note). Minor redundancy exists between the first and third sentences both emphasizing that this is schema-only.

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?

With no output schema, the description does a good job explaining that the return value is a schema definition and lists the kinds of fields it contains. It is complete enough for a simple one-parameter read, though the ambiguous 'declare' phrasing slightly muddies the intended use.

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% and the single parameter title_id is fully documented in the schema. The description does not add any meaning beyond what the schema already provides, 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 description names a specific verb and resource — 'GET ONLY the UserCustomData field of TitlePublicConfigurationModel' — and distinguishes the schema from actual per-user values. It differentiates from siblings like get_title_custom_data by naming the exact field, though it does not explicitly reference alternatives.

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 implies when to use it by contrasting schema with actual per-user values ('actual per-user values live on the User document') and suggesting use for declaring player-specific stats. However, it never explicitly names the alternative tools (e.g., save_user_custom_data, get_title_custom_data) or states when not to use this tool.

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