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

Annotations declare idempotentHint=false, but the description explicitly claims mode=open is idempotent ('幂等开户'), a direct conflict on the same operation. Beyond that conflict, the description does add useful context (credits-based accounts, a mode-scoped read versus a mode-scoped write), but the idempotency claim an agent would rely on for safe retries is contradicted by the structured metadata.

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 two short, front-loaded sentences covering purpose and mode semantics. The inline example duplicates the schema's examples array, which is minor waste, but nothing else is extraneous.

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 2-parameter tool with full schema coverage and annotations, the description covers purpose and modes adequately. It omits what an open or balance call returns (no output schema exists) and leaves the boundary with settlement.ledger and settlement.transfer unaddressed, and the idempotency mismatch undermines an agent's ability to reason about safe retries.

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%: both mode (with an enum and per-value descriptions) and account_id are fully documented in the schema. The description restates the mode semantics but adds nothing new, so the baseline of 3 applies.

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 a specific verb and resource combination ('开立或查询跨 Agent 结算账户（credits）') and splits the behavior by mode (open vs balance), so an agent knows exactly what the tool does. It does not distinguish this tool from the sibling settlement.ledger and settlement.transfer tools, which keeps it below a 5.

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?

Mode selection is covered: mode=open opens an account idempotently, mode=balance queries balance, which implies the two use cases. However, there is no guidance on when to choose this tool instead of settlement.transfer (to move funds) or settlement.ledger (to read history), and no prerequisites are stated.

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