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

The description says mode=open is idempotent and returns the existing account if already present, but the annotations declare idempotentHint=false. That is a direct contradiction on a retry-safety behavior, which is material for an agent deciding whether it can safely repeat the call.

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 front-loaded with the two modes and their behavior, and the business context is relevant. The embedded example duplicates the schema example, so there is minor redundancy.

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 still explains what open returns (existing account and balance) and what balance mode does. It covers initial balance and funding routes, though the idempotency contradiction undermines completeness around retry behavior.

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 already 100%, so the baseline is 3. The description adds useful meaning beyond the schema: mode=open is idempotent, balance mode queries funds, and account_id corresponds to an Agent name or organization ID.

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 states specific verbs (open/query) and the resource (cross-Agent settlement account), then splits behavior by mode=open vs mode=balance. It also distinguishes itself from settlement.transfer and settlement.credit, so an agent can identify the tool 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 explicitly maps mode values to actions and explains that funding comes via settlement.credit or settlement.transfer. It does not state when to use settlement.ledger instead or any when-not conditions, so it falls short of full routing guidance.

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