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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered structurally. The description adds the meaningful behavioral point that this is account-scoped and that affordability requires pairing it with a quote_* call. It stops short of noting any staleness or refresh behavior, but nothing essential is missing.

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, front-loaded with the trigger condition and followed by the complementary pricing tools. No redundant restatement of the title and 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?

Return shape need not be described because an output schema exists, and the description covers purpose, trigger, and the related pricing calls. It leaves only minor ambiguity around whether the balance is personal or team-level, which is a small gap for a trivial no-arg read tool.

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 there is no parameter semantics to explain; the baseline for a no-arg tool applies. The description correctly frames the call as requiring no input.

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 ('returns the credits available on their account') and implicitly differentiates from the quote_* siblings, which return prices rather than balance. An agent can tell exactly what this tool yields 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?

Gives two explicit trigger conditions: when the user asks how many credits remain, and as a pre-check before proposing a creation they may not be able to afford. It also names the correct alternatives for pricing (quote_image, quote_video, quote_voiceover), so the agent knows where to route price questions instead.

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