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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds a genuinely useful behavioral fact: the model assumes a constant monthly growth rate, which tells the agent results are idealized projections. It does not state the return shape, and with no output schema that gap remains.

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 sentence with zero waste, front-loading the operation, the model assumption, and the horizon. Nothing to trim and nothing buried.

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 three-parameter arithmetic projection with no output schema, the description covers the core intent but says nothing about what the response contains (per-month series vs. final figure) or whether growth is simple or compounded. Those omissions matter for correctly consuming the result.

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 0%, but the parameter names (currentGb, monthlyGrowthPercent, months) are self-describing and carry units. The description echoes the concepts implicitly ('storage size', 'monthly growth rate', 'up to 120 months') without adding format or interpretation detail beyond what the names and numeric bounds already convey.

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 and resource ('Project storage size') plus the projection model and horizon, so an agent knows it is a forecast calculator rather than a lookup. It does not explicitly distinguish itself from the closest sibling, estimate_backup_retention, which also projects forward.

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 gives no when-to-use guidance, no prerequisites, and never names an alternative. An agent must infer from the name alone when this beats estimate_backup_retention or a manual calculation.

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