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

Annotations already declare readOnlyHint=true, and the description adds meaningful behavioral context: it corrects for OS/filesystem overhead and is backed by Cleanor Labs measured per-item sizes. This clarifies data provenance and the calculator's accuracy, going beyond the safety annotation without contradiction.

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 core function, the data source, and concrete use cases. No fluff, front-loaded with the main question it answers.

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 simple two-parameter tool with an output schema, the description fully covers the tool's purpose, key corrections, and typical applications. The annotations cover safety, and the schema covers parameters and output, so no critical context is missing.

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%, but the description adds semantic value by explaining that the storage size is interpreted as advertised capacity and the result is corrected for real overhead. It also explicitly mentions 'photos or minutes of video', aligning with the content enum and clarifying the meaning of the output.

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 tool's function: calculating how many photos or minutes of video fit in a storage size, with a specific verb ('fit') and resource ('storage size'). It also distinguishes itself from siblings by focusing on corrected/realistic capacity rather than generic conversion tools.

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 explicit use cases: 'Use for realistic sample copy, dashboards, or "how many photos fit in 128 GB" answers.' It doesn't mention alternatives or exclusions, but given no sibling tool overlaps significantly, the guidance is clear and practical.

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