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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds context not in the structured fields: the cost ('1 credit') and the shape of the response (formatted labels, unit names, scaled numeric values). Return-value detail is partly redundant given an output schema exists, which keeps this out of the top score.

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 body is two tight sentences plus a short cost note, and the key capability is front-loaded. The only waste is the redundant name/title repetition at the start ('File Size Formatter: File Size Formatter'), which adds no information.

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 pure-function tool with one required parameter, full schema coverage, an output schema, and read-only annotations, the definition covers purpose, inputs, outputs, and cost. The remaining gap is disambiguation from related conversion tools, which would make it fully complete.

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% and every parameter is documented in the input schema, including defaults and the binary/decimal distinction. The description only echoes 'optional precision and unit settings' without adding meaning such as how auto unit selection behaves or what happens with precision=0. Baseline 3 applies when the schema does the heavy lifting.

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 states a specific verb and resource: it 'converts raw byte counts into human-readable file size strings.' That is unambiguous and clearly distinct from neighbors like UnitConverter or NumberBaseConverter. It loses a point only because it opens by restating the name and title verbatim before getting to the actual meaning.

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?

Usage is implied by 'Send a byte count with optional precision and unit settings,' which tells the agent the required input shape. However, there is no explicit when-to-use or when-not-to-use guidance, and no mention of the obvious alternative (UnitConverter) that an agent might weigh against this tool.

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