A subaccount's balances (from the ledger)

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and repeatability are covered. The description adds value beyond them by disclosing the content of the read — pending, available and settling balances sourced from the ledger — which matters because there is no output schema to reveal the return shape.

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?

It is short and front-loaded, but the first sentence is a near-verbatim restatement of the title, and 'from the ledger' appears twice in two sentences. Roughly half the text is redundant repetition rather than new information.

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 one-parameter read tool with no output schema, the definition covers what is read and from where, which is the minimum an agent needs. It still omits the distinction from the sibling get_balance and any note on balance freshness or currency, leaving a gap on the main selection decision.

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 `id` parameter is documented as the subaccount id with the `sub_…` prefix pattern. The description adds no further parameter meaning such as where to obtain the id or whether a non-subaccount id errors, so the schema does all the work.

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 (read) and resource (a subaccount's pending, available and settling balances) and notes the ledger as the source, so the agent can tell it returns balance figures for one subaccount. It does not name or distinguish itself from the sibling get_balance, which is likely the account-level counterpart, so the differentiation is left implicit.

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?

There is no explicit when-to-use guidance: nothing says to call this for a `sub_…` id versus get_balance for the top-level account, nor any prerequisite (e.g., the subaccount must exist or be active). Usage is only inferable from the resource name and the required `id` parameter.

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