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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds significant behavioral insight: the extra transaction scan cost, the meaning of transactions_basis, the payment-cycle caveat, the absence of paid/status fields, and the batch response shape. All of this goes well beyond the annotations.

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 long but each sentence carries essential context for correct invocation. It front-loads the core return shape, then layers optional behaviors and caveats clearly. The structured paragraphs and parentheticals keep heavy information navigable.

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?

Given there is no output schema, the description does a strong job of covering return fields, batch shape, error shape, and available fallback behavior. It is still missing detail on transactions_detail, and the exact structure of individual transaction entries is only partially implied, a minor but real gap.

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 0% schema description coverage, the description correctly compensates for bill_ids, account_id, and include_transactions, explaining their roles and constraints. However, it never mentions transactions_detail or its compact/rich/raw enum values, leaving a relevant optional parameter undocumented.

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 clearly states the operation: returns bill-level detail for credit card bills by id via GET /bills/:id, and lists exact fields. It also distinguishes itself from sibling tools such as openfinance_list_credit_card_bills and openfinance_list_transactions, so there is no ambiguity about scope.

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 description gives explicit when-to-use guidance: use openfinance_list_credit_card_bills first to discover bill_ids, pass include_transactions with account_id for itemized purchases, and prefer the sibling list tool when paid status is needed. It also tells the agent when NOT to manually rebuild totalAmount and how to fetch transactions independently.

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