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

Beyond annotations (readOnlyHint, idempotentHint), the description discloses that account_url is read-only and cannot sign anyone in, and that account_key grants full account takeover if exposed. These security and access implications are not in the annotations.

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 detailed but every sentence earns its place: it lists return values, usage triggers, and critical handling notes in a logical order. The security warning is front-loaded with the key explanation.

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?

Given no output schema, the description fully covers the return fields and their semantics, plus when to call the tool and how to present results. An agent has all necessary context to invoke it correctly.

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 has zero parameters, so there is nothing to document. The description instead clarifies the meaning of the return fields (has_paid, account_url, account_key), which is valuable given the absence of an output 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 the tool's purpose: it provides account credits, order eligibility, a link to the account page, and a transfer key. It distinguishes itself from siblings by focusing on account state rather than video creation or job management.

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?

Explicit guidance is given: call before the first kleo_create_video and when users ask about credits, how to get more, or cross-device usage. It also instructs how to handle sensitive output (show account_key only on request).

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