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

Annotations already establish readOnly=false-free safety profile (readOnlyHint true, idempotent, closed-world), so the description's job is to add substance — and it does, disclosing that the result enumerates both balances plus every reconciling item, and that it surfaces blocking conditions. That is real content beyond the annotations, though it stops short of saying what happens for an unknown account or a statement-free period.

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 tight sentences with no filler, and the output content is front-loaded. The elliptical first clause costs a little comprehension, but nothing is padded or restated.

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?

With no output schema, the description must carry the return-value burden, and it does partially by naming the balances, the itemized reconciling entries, and blocker reporting. It still omits what a blocker looks like, empty/unreconciled outcomes, and how the result relates to rec_signoffs, leaving gaps for a no-output-schema 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?

Schema description coverage is 100%, so account, through, and currency are fully documented in the schema, and the description only loosely echoes two of them ('an account through a statement's last day'). Baseline 3 is correct — the description adds no syntax, default, or edge-case nuance beyond the schema.

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 conveys what the tool produces — a statement balance, a book balance, the reconciling items between them, and what blocks sign-off — but it does so as a subject-less noun fragment ('An account through a statement's last day'), with no verb stating the operation. It also fails to distinguish itself from close siblings like rec_signoffs, rec_matches, and rec_candidates, which a reader could easily confuse with it.

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 instruction and no named alternative. The trailing phrase 'Says what blocks a sign-off' only weakly implies it is a pre-sign-off diagnostic, leaving the agent to infer its place relative to rec_sign_off and rec_matches. No exclusions or prerequisites are given.

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