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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered, but the description adds real domain behavior: movements are returned newest first, each carries state reserved/charged/refunded with price and resulting balance, and plan credits are spent first and lapse at month end. It stops short of noting any cost, rate limits, or what happens when the account has no activity.

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?

Every clause carries relevant information, but it is delivered as one long run-on sentence stacked with parentheticals, so the headline idea (credit statement) is buried under enumeration. Splitting the aggregates, the movements list, and the plan-credit rules into distinct sentences would make it far easier to scan.

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 and only one optional parameter, the description must carry the return shape itself, and it does so thoroughly by listing the fields, the state values, and the ordering. Minor omissions remain: currency/units and the behavior when no movements exist are unstated.

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 'limit' is already documented as the count of latest movements, but the description clarifies that the cap applies specifically to movements (newest first) rather than truncating the aggregate balance figures or the plan-credit list. That scoping detail adds genuine meaning 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 names a single, specific resource — the account's credit statement — and enumerates exactly what it reports (available, reserved, spent, refunded, granted, expired credits, latest movements, plan credits). That is far more specific than the bare name 'get_credits'. It does not explicitly contrast with siblings like get_account or get_price, which is the only gap.

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?

The text is entirely about content; it never states when to reach for this tool versus get_account, get_price, or list_jobs, and gives no prerequisites or exclusions. An agent can only infer usage from the resource name, and get_account could plausibly also surface credit information, leaving the choice ambiguous.

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