Get Subaccount Balances

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

No annotations are provided, so the description carries the full burden. It discloses authentication requirements and the primary-account restriction, adding valuable context. The word 'Fetch' implies a read-only operation, though it does not detail return format or potential side effects, which is acceptable for a simple getter.

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 two sentences with no wasted words. It front-loads the purpose and then adds constraints, making it easy to parse quickly.

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?

For a parameterless fetch tool, the description covers what it does, its scope, and prerequisites. There is no output schema, but the return is implied as balances. A minor gap is the lack of response structure detail, but overall it is sufficient for selection.

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, and schema coverage is trivially 100%. Per the rubric, zero-parameter tools receive a baseline of 4. No further parameter explanation is needed.

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 'Fetch balances by currency and account type (SPOT and FUTURES) for each account in the account group.' The verb 'Fetch' plus the resource and scope distinguishes it from sibling tools like get_balances, which likely target a single account.

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 explicitly notes 'Only functional for a primary account' and requires API keys, providing clear usage context. It does not name alternatives, but the account-group scope implies use when needing consolidated balances across the group rather than a single subaccount.

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