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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false, so the safety profile is fully covered. The description adds meaningful context about what the returned credits mean and confirms this is a current-state read. No contradiction with annotations exists.

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 main result is front-loaded in a single focused sentence, with compact parenthetical definitions for the fields and a direct parameter condition. Every phrase earns its place; there is no filler.

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 one optional parameter, a full output schema, and strong read-only/idempotent annotations, the description provides everything an agent needs to select and invoke the tool correctly. It covers field semantics and the only parameter condition without requiring extra context.

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 schema already documents website_id with 100% coverage, including that it comes from get_account and is optional for single-website accounts. The description restates this guidance ('Pass website_id when the account has several websites') without adding new format, constraints, or defaults.

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 uses a specific verb ('Returns') and a clear resource ('the website's current credit balances'), and it enumerates the exact fields returned: ai_brain_credits, articles_credit, backlink_credits, and has_active_subscription. This makes the tool's purpose unambiguous and distinguishes it from all sibling tools.

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 gives clear context for invocation by stating when to pass website_id ('when the account has several websites') and directs the agent to get_account for the id. It does not explicitly contrast alternatives, but no sibling tool appears to perform the same credit-balance lookup.

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