Your overall position

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

Annotations already declare the operation read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds useful behavioral context by specifying the aggregate scope across every group and friend and the one-line-per-currency output shape, which goes 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 concise and well-structured: it immediately states the aggregate scope and output granularity, then provides example queries and a forward reference to the relevant sibling. Every sentence earns its place with no filler.

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 are no parameters, strong annotations, an output schema, and a description that covers purpose, scope, output shape, usage examples, and the primary alternative, nothing critical is missing for an agent to select and invoke the tool 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?

The tool has zero parameters, so there are no argument semantics to document. With no params, the baseline is 4, and the description does not need to compensate for schema gaps since schema coverage is complete and there is nothing to configure.

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 function: reporting everything owed and owed to the user across all groups and friends, aggregated one line per currency. It gives concrete example queries and explicitly differentiates itself from explain_balance, which drills into a single group.

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 use cases such as "how much do I owe overall", "who owes me money", and "what is my total exposure". It also gives clear routing guidance by telling the agent to start here before drilling into one group with explain_balance.

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