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

With readOnlyHint=true present, the description adds context about the virtual account types, currency handling, and the effect of each direction on receivable/payable, which is valuable. It does not overdo it; a 4 is justified because it goes beyond the annotation without contradicting it.

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 a few sentences but packed with essential information about directions and virtual accounts; it is somewhat long but every part adds value. Front-loads the core purpose well.

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 explains the return structure (directions, virtualAccount fields) indirectly, but doesn't explicitly state that it returns a list or how amount is formatted beyond major units. It is fairly complete for a simple tool.

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% and the description elaborates on the single parameter, explaining the filtering behavior and how to resolve names, adding significant 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 clearly states the purpose: retrieving an IOU/debt ledger, specifying the directional labels and virtual account fields. It also distinguishes itself from run_read_query, though no sibling has 'get_iou' in its name.

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 says to use for questions about who owes whom, outstanding debts, or IOU history, and notes that this data is not visible via run_read_query. It also explains the optional counterpartyId filter and how to resolve names via run_read_query.

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