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

With no annotations, the description is the sole source for behavioral traits. It does not disclose rounding rules, precision, handling of edge cases (e.g., zero rate, negative time beyond schema constraints), or return format. The output schema exists but isn't mentioned.

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 extremely brief (one sentence) but lacks important context. It under-specifies rather than being concise, missing opportunities to add value in a few additional 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?

Despite low complexity, the description omits usage context, return value description, and differentiation from similar tools. An output schema exists, but the description should still provide enough information for an agent to decide when to invoke this tool.

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% with each parameter described (principal, rate, time). The description adds no additional meaning beyond the schema, warranting a baseline score of 3.

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 'Calculate simple interest' clearly states the verb and resource. However, it does not differentiate from sibling tools like compound_interest or loan_payment, which are related but distinct.

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?

No guidance on when to use this tool versus alternatives. For instance, it doesn't mention that compound interest uses compounding periods or that other tools might be more suitable for specific scenarios.

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