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

With no annotations, the description carries the full burden but only states it computes growth. It omits compounding frequency assumed, whether rate is a percentage or decimal (beyond the schema hint), and what the return looks like. A mutation-free calculator needs less, but key behavioral assumptions go unstated.

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?

A single short front-loaded sentence that is efficient but under-specified; it earns its place yet leaves obvious gaps that could have been filled in the same sentence.

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 4-parameter financial calculator with no annotations, no output schema, and two undocumented parameters, the description is too thin to let an agent call it confidently. It should specify compounding assumptions, rate format, and the years unit.

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 only 50%: rate and contributions are described in the schema, but principal and years are bare, and the description adds no parameter meaning at all. It doesn't compensate for the coverage gap, e.g. by clarifying units for years or how contributions compound.

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?

States a specific verb (Calculate) and resource (compound interest) with scope (growth over time), which distinguishes it from sibling calculators like loan_calculator or mortgage_calculator. It doesn't explicitly name an alternative or clarify it's the general-purpose compounding tool, but an agent can select it correctly.

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?

There is no guidance on when to use this versus loan_calculator, mortgage_calculator, or percentage_calculator, nor any prerequisites. The agent must infer from the name alone that this is the recurring-growth tool.

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