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

Annotations already declare read-only and idempotent behavior. The description adds behavioral detail beyond annotations by stating the tool supports both formatting (bytes to string) and parsing (string to bytes), and specifies the exact unit systems. No contradictions with annotations.

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 two concise sentences. The first sentence states the core transformation in both directions, and the second lists the covered units. No redundant or filler text.

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?

The tool is simple, the schema covers all parameters, annotations cover safety, and an output schema exists, so the description need not explain return values. The description fully captures the tool's scope and standards, making it complete for an agent to select and use 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 coverage is 100% with descriptions for all three parameters. The description adds value by defining the SI and IEC standards explicitly (KB=1000, KiB=1024), which clarifies the 'standard' enum, and by explaining that 'size_string' is for parsing back to bytes—enhancing the schema's brief parameter comments.

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 uses a specific verb and resource: 'Convert raw byte counts to human-readable sizes... or parse size strings back to bytes.' It clearly identifies the tool's dual functionality and the unit standards (SI vs IEC), distinguishing it from generic formatting or 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 provides clear context by explaining the two output standards (KB=1000, KiB=1024) and the range of units covered, which implies when to use each. It does not explicitly exclude alternatives, but for a single-purpose utility this is sufficient context.

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