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

Annotations already establish read-only, idempotent, non-destructive behavior, so the description does not need to restate safety. It adds behavioral context by showing the register is valued 'at as_of', includes interim interest/next-payment figures, and is totalled per currency, plus noting the free access tier. This complements rather than contradicts 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?

Two sentences with no filler. The key output fields are front-loaded, and the alternative tool is mentioned in a compact second sentence. Every element 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?

For a read-only listing tool with no output schema, the description enumerates the computed output fields, notes currency totals, and mentions the alternative Pro roll-up. All four optional parameters are fully documented in the schema, so 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%, so the baseline is 3. The description adds meaning by tying as_of to valuation of balances and interest, and by clarifying that results are totalled per currency, which enriches the currency parameter beyond its schema filter description.

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 uses a specific verb and resource ('List the loan register') and explicitly enumerates the returned fields: terms, level payment, effective annual rate, periods paid, balance, interest to date, and next payment. It differentiates itself from the sibling loans_report by noting this is the free detail view while loans_report is the Pro roll-up.

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 clearly states this is the free version and points to loans_report as the Pro roll-up alternative, giving agents a decision cue based on whether a rolled-up view is needed. It does not explicitly discuss other siblings like loan_schedule, but the context is clear enough for choosing between the two most similar list/report tools.

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