get_credit_card_bills

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

Annotations include readOnlyHint=true, which the description respects ('Returns'). The description adds behavioral context beyond the annotation by specifying that it returns both open and past bills and lists relevant fields (total amount, minimum payment, due date). However, it does not mention potential pagination or consent requirements, which would be useful in an Open Finance context.

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 well-structured with purpose, args, and returns sections. It front-loads the core functionality and provides parameter explanations. Minor redundancy exists (the Returns section restates the opening line), and the extra ctx parameter adds noise, but overall it is efficient and organized.

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 the output schema exists, the description need not detail return values. It covers prerequisites and parameter semantics. Missing context includes consent requirements (common in Open Finance Brasil) and pagination behavior, but these are partially implied by sibling tools. Thus it is sufficiently complete for straightforward invocation.

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 description coverage is 0%, so the description must compensate. It explains all three schema parameters: subject_id as 'User's CPF', bank as 'Identifier of the participating bank', and credit_card_account_id as 'ID returned by list_credit_cards'. However, it also lists a 'ctx' argument not present in the input schema, which could confuse an agent about what to pass.

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 tool's purpose with a specific verb ('Returns'), a specific resource ('bills (open and past) of a credit card'), and context ('via Open Finance Brasil'). It also includes key fields returned (total amount, minimum payment, due date). This distinguishes it from sibling tools like list_credit_cards and list_transactions.

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 implies usage context by noting that credit_card_account_id is 'ID returned by list_credit_cards', which establishes a prerequisite and invocation order. However, it does not explicitly state when to use this tool over alternatives or provide exclusions, so it falls slightly short of full guidance.

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