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

Even though readOnlyHint=true is already in annotations, the description adds meaningful behavioral detail beyond that: it defines the four direction labels and their effect on receivable/payable balances, explains virtualAccount.type and currency, and notes that amount is in major units. This goes well beyond a mere read-only declaration.

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 dense but not bloated; the core purpose and scope are front-loaded in the first sentence. The later sentences explain transfer semantics, virtual account fields, and units, all of which are necessary for correct interpretation. Slightly verbose, but every clause earns its place.

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?

The tool has one optional parameterchers and no output schema, yet the description fully covers what the ledger contains, the meaning of each entry direction, the virtualAccount fields, units, and the filtering option. It also addresses the primary alternative. Nothing essential is missing for an agent to call it correctly.

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 counterpartyId parameter is already described with filtering semantics and how to resolve names via run_read_query. The description only briefly reinforces "or one, via counterpartyId," adding little beyond the schema. Baseline 3 is appropriate.

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 begins with a specific verb and resource: "Get the user's IOU/debt ledger," then defines the scope as who owes the user and whom the user owes. It also differentiates itself from run_read_query by explicitly stating this data is not visible there, so an agent can distinguish it from the closest sibling.

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 provides explicit usage guidance: "Use this for any question about who owes whom, outstanding debts, or IOU history." It also names the alternative and explains the boundary: "this data is not visible via run_read_query." This gives the agent clear when-to-use and when-not-to-use context.

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