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

The description adds meaningful behavioral context beyond the annotations: it states that already-posted periods are never duplicated, making repeated calls safe. This complements the idempotentHint annotation with a concrete explanation of the idempotency mechanism. It also clarifies the save-vs-preview behavior, which is not fully captured by annotations alone.

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 sentences, each earning its place: the first states the core action and scope, the second explains idempotency safety, and the third routes to the preview alternative. No wasted words.

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 zero-parameter tool with an output schema and annotations covering idempotency and destructiveness, the description is nearly complete. It could mention what the output contains or whether the operation is reversible, but the output schema likely covers return values, and the idempotency statement already addresses the main safety concern.

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 the schema provides no parameter semantics to clarify. The description compensates by explaining the scope of the operation ('all deposit and savings accounts up to today'), which is the only semantic an agent needs. Baseline 4 for zero-parameter tools 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 clearly states the action ('Calculates and saves interest'), the resource ('all deposit and savings accounts'), and the temporal scope ('up to today'). It also distinguishes itself from the sibling preview_interest by noting that this tool saves while preview_interest only shows amounts.

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?

The description explicitly says when to use this tool (to post interest) and names the alternative (preview_interest) for when you want to see amounts without saving. This gives an agent clear routing guidance.

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