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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds an explicit 'SIDE EFFECTS: None (pure mathematical calculation)' statement, reinforcing that no external state changes or side effects occur. This is useful context beyond the annotations, though not extensive.

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 tightly structured with labeled sections: PURPOSE, WHEN TO USE, WHEN NOT TO USE, and SIDE EFFECTS. Each section is a single focused sentence with no filler. The most important decision-making information is front-loaded.

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 calculation tool with a rich input schema and an output schema, the description covers purpose, usage conditions, exclusions, alternative tool routing, and side effects. There are no gaps that would prevent an agent from selecting and invoking this tool 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 description coverage is 100%, so the baseline is 3. The schema already documents monthly_api_spend_usd and target_tier with meaningful descriptions including tier prices. The tool description does not add additional parameter-level guidance, but it does provide broader context about the calculation that the parameters feed into.

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 opens with a specific verb and resource: 'Calculates CapEx payback timeline and token savings comparing on-premise Aradia hardware against recurring cloud LLM API expenditures.' It clearly distinguishes from the sibling query_hardware_specs by mentioning financial justification rather than raw specifications.

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?

Explicit WHEN TO USE and WHEN NOT TO USE sections are provided. The description says to use it for financial justification reports for CFOs, warns against using it when API spend is unknown or zero, and directs users to query_hardware_specs for raw specs. This leaves no ambiguity about tool selection.

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