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

Annotations already establish readOnlyHint/idempotentHint/openWorldHint=false, but the description adds substantial context beyond them: account_url opens a read-only page that cannot sign anyone in, and account_key is a credential that lets anyone take over the account and spend its credits, with guidance to reveal it only on request. These are meaningful safety and disclosure behaviors the annotations do not convey.

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?

Information is front-loaded (what it returns first, then when to call, then disclosure guidance) and every sentence carries content. It is somewhat dense and run-on, with heavy parenthetical nesting, which costs a point on structure.

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 steps in to explain all returned values and their meaning, plus the security nuance around account_key. An agent has everything needed to call it and to present results safely.

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?

The tool takes zero parameters, so per the rubric the baseline is 4. The description instead documents the semantics of the returned fields (credit meaning, film_trial vs has_paid, referral mechanics), which is valuable but not parameter semantics.

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 the specific resource (this account) and enumerates exactly what it returns: remaining credits, whether a FILM can be ordered (has_paid/film_trial), the animatic allowance, referral/invitation link, account page URL, and the Kleo key. This is far more precise than the title 'Account and credits' and clearly distinguishes it from siblings like kleo_create_video.

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?

It states explicit triggers ('call it before the first kleo_create_video of a conversation') and user-intent conditions (asking about credits, how to get more, how to use Kleo elsewhere), and names a sibling tool. When-to-use is unambiguous.

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