Settle up

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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent, open-world write. The description adds real value by clarifying the operation is record-only and does not transfer funds, plus the balance-settling semantics. It stops short of describing what happens if no outstanding balance exists, whether the record is reversible, or how identities are resolved.

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?

Three short sentences, front-loaded with the core purpose, then the key caveat, then the balance-omission rule. No filler or redundancy.

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 7-parameter mutation tool with no output schema, the description covers the essential behavioral nuance (record-only, full-balance settlement) that an agent needs to invoke it correctly. Minor gaps remain around error behavior and multi-currency requirements, which live partly in the schema.

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 86%, so the baseline is 3, but the description goes further by explaining the interaction between omitting 'amount' and the presence of 'group' — meaning that is not expressed in the schema. It does not clarify accepted identifier forms for 'from'/'to' beyond what the schema already says.

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 ('Records a payment from one person to another') and disambiguates the concept with 'This does not move money; it records that money changed hands.' It does not explicitly name the nearest sibling (create_expense) as a contrasting option, so it falls short of full sibling differentiation.

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 useful conditional guidance for the amount parameter: omit it to settle the full balance, scoped to a group if supplied, otherwise the overall friend balance. However, there is no guidance on when to choose settle_up versus create_expense or get_balances, and no stated preconditions or exclusions.

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