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

Annotations already cover read-only, idempotent, non-destructive. The description adds genuinely useful behavior beyond that: it is free, needs no sign-in, and crucially that the response differs by auth state (full price list when signed out vs. account-specific offering when signed in). This auth-dependent branching is exactly the kind of context annotations can't express.

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?

It's a single dense sentence that is front-loaded with the core purpose, which is good, but the latter half is a run-on clause stacking auth-state behavior and model-id usage. It earns its content but readability suffers from over-packing.

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?

No output schema, so the description carries return-value burden, and it does explain what comes back (qualities, per-unit credit costs, plan-lock status, model ids). Missing details like pagination or the shape of the plan-lock field, but largely complete for a zero-parameter catalog list.

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 is 100% and the single kind parameter with an enum is fully documented in the schema. The description doesn't elaborate on the parameter semantics, but baseline 3 is appropriate given the schema does the heavy lifting.

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?

States a specific verb (lists) and resource (what UGCFans makes at each quality, with credit prices), and distinguishes it from siblings by naming that it feeds estimate and the make tools with model ids. An agent can tell this is the catalog/discovery tool, not a make or estimate tool.

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?

Conveys when to use it – free, no sign-in needed, and it's the source of model ids for ugcfans_estimate and make tools. It doesn't explicitly name exclusions or contrast against siblings that also return model info, but the routing role is clear.

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