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

Annotations already declare readOnlyHint=true, yet the description adds substantive behavior beyond them: `balance` is always the whole credit line and is explicitly NOT filtered by the date range, and the tool is scoped to the caller's own credit line with no account parameter. It also discloses the auth prerequisite (partner credit-line session) and the guest-session limitation, which the annotations do not cover.

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 definition is a single dense paragraph but the most decision-relevant facts (what it returns, balance-not-filtered caveat, read-only, auth requirement, no account identifier) are front-loaded. The long enumeration of row fields is verbose, though it substitutes for a missing output schema.

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 available, the description fully spells out the return shape: top-level balance and account fields plus every row field including bucket semantics (`current` vs `pending`) and lineType (`booking` vs `cancellation_fee`). Auth requirements, defaults, and range limits are all covered, leaving nothing an agent needs to call it correctly.

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 coverage is 100%, so both date parameters are already documented, making 3 the baseline. The description still adds meaning by framing `from`/`to` as due-date bounds with a default of the current month and a 93-day cap, and by implying the `sessionToken` is irrelevant here since guest sessions have no credit line.

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 names a specific verb and resource ("Returns the signed-in partner's own credit-line statement") and immediately enumerates the three components returned: balance, account details, and booking rows. Combined with the note that it takes no account identifier, an agent can distinguish this from sibling tools like list_settlements or get_statement_document 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?

It gives clear conditions for use: requires a signed-in partner credit-line session, guest sessions have no credit line, and the date range defaults to the current month with a 93-day ceiling. It stops short of naming alternatives, so it never explicitly says when to prefer get_statement_document or list_settlements instead.

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