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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), so the bar is lower. The description adds the useful scope hint that results can be global or scoped to a single contact, but says nothing about pagination, ordering, or the shape of the owed/owing direction 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?

Single front-loaded sentence with no filler; the trigger condition leads. Slightly conversational in tone ('who owes whom and how much') but every clause carries meaning.

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?

With an output schema present and full parameter coverage, the description needn't explain return values. It is adequate for a simple, read-only list tool, though it could note ordering or whether settled debts are included.

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 100% and there is only one optional parameter, so the schema already documents contact_id. The description's 'either overall or with one contact' phrasing reinforces the optional-filter semantics but adds no format or syntax detail 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 states a specific verb and resource: listing debts ('money owed', 'who owes whom and how much'). The scope is clear (overall or filtered by one contact), though it does not explicitly contrast itself with sibling debts.create/update/delete beyond what the names already imply.

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 gives a clear trigger condition ('when the user asks about money owed, either overall or with one contact'), which maps directly to the optional contact_id filter. No explicit when-not guidance or named alternative is provided, keeping it short of a 5.

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