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

Annotations already declare readOnlyHint=true and destructiveHint=false, so "Read-only" is redundant, but the description goes further by disclosing the response envelope (`settlements[]`, `payable[]`, `bank`, `notice`) and an obligation the agent must honour: the `notice` must be shown as given, and overpayments become credit rather than refunds. The one blemish is that it says guest sessions have no credit line while the schema still advertises an optional guest `sessionToken`, leaving a small inconsistency unresolved.

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 purpose and return envelope are front-loaded, and the enumeration of fields is genuinely useful given there is no output schema. It is dense but each clause carries information; only the redundant "Read-only" could be cut.

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?

No output schema exists, yet the description enumerates every returned field including statuses and lifecycle fields (`expiresAt`, `receivedAmount`/`receivedAt`). Combined with the session prerequisite and the sibling disambiguation, an agent has everything needed to call and interpret this 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?

With a single parameter at 100% schema coverage, the schema already explains `sessionToken`. The description adds only indirect context about sessions (partner session required, guest sessions lack a credit line), which actually muddies rather than clarifies the optional guest token's role. Baseline 3 fits.

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?

Opens with a specific verb and scoped resource: "Lists the signed-in partner's own bank-transfer settlements of the credit line." It also pre-empts confusion with the closest sibling by stating outright that per-booking payment state lives on rows of `get_credit_line_statement`.

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?

Explicitly routes the agent: this tool is for the list of transfers, `get_credit_line_statement` is for per-booking payment state. It also names the prerequisite condition (signed-in partner credit-line session) and the excluded case (guest sessions have no credit line).

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