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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, and the description's 'Read-only; no credits spent' largely restates that. It adds little behavioral detail beyond annotations, though it does indicate the response includes plan allotment and recent transactions, which is useful framing.

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?

Two sentences, zero filler: the first defines the payload, the second gives the triggering condition. The scoping and safety note are front-loaded rather than buried.

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?

Annotations cover the safety profile and an output schema exists, so the description doesn't need to explain return values. For a zero-required-parameter read tool, nothing an agent needs to call it correctly is missing.

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 description coverage is 100% and the single optional 'limit' parameter is fully documented in the schema, so the description need not restate it. It adds no syntax or default guidance beyond what the schema supplies, matching the baseline.

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 and resource ('Check the account's current credit balance, plan allotment, and recent credit transactions'), which cleanly separates it from siblings like buy_credits and estimate_snack_cost. An agent knows exactly what it retrieves without opening the schema.

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?

Explicitly says when to call it ('before a credit-spending generation') and names the specific spending tools it should precede (create_video, generate_snacks, studio_*, seedance_*, etc.). This is a model routing instruction rather than vague context.

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