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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds genuinely non-structured context: this is a cost-free call and it returns credit state, expiry timing, plan, and admission status. It stops short of describing refresh timing or what happens when credits are exhausted.

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?

A single front-loaded sentence naming the resource first, then enumerating returned fields. Dense but every clause maps to a distinct return value; the trailing 'Free.' is terse but earns its place as a cost signal.

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 input parameters and no output schema, the description carries the return-value burden and does enumerate the key fields (credits left/granted/spent, expiry, plan, admission). It is nearly complete for a zero-arg status tool, lacking only format details such as units or expiry date style.

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?

Zero parameters, so the baseline of 4 applies; there is no argument surface for the description to explain. The implicit subject ('the signed-in account') correctly tells the agent no identifier needs to be supplied.

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 ('Shows') and a specific resource (the signed-in account's credits, expiry, plan, and UGCFans admission status). Among a sibling set dominated by generation tools (make_video, make_image, estimate), this is unambiguously the account-status read 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?

Usage is implied rather than stated — the trailing 'Free.' signals this costs no credits, which is a mild routing hint against paid siblings like estimate or make_video. However, no explicit when-to-use condition or named alternative is given.

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