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

Annotations already establish readOnly/idempotent/non-destructive, so safety is covered. The description adds genuinely useful behavioral context beyond them: pricing ('free'), error semantics (returns isError on invalid input or upstream failure, not charged), the conversion-table source, and the binary convention (1 GB = 1024 MB). It does not describe rate limits or return shape, but the error/charging disclosure is meaningful added value.

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?

Front-loads the purpose, then supporting detail (abbreviations), then operational notes (price, errors). Dense but every sentence contributes; the long unit enumeration is the only slightly padded element, though it usefully scopes coverage.

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?

With an output schema present, return values need not be explained, and the description covers purpose, accepted inputs, error behavior and cost. It is nearly complete for a simple converter, with only the overlap against time_convert left unaddressed.

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%, so each parameter is already documented and the baseline is 3. The description adds meaning beyond the schema: concrete abbreviation examples (mi, degF, GB, knot...), the binary data-size definition, and the special semantics of omitting 'to' to enumerate all compatible units.

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 (Convert) and resource (units) and enumerates the covered categories, plus a distinct second mode ('list every unit a value converts to'). It is clear what the tool does, but it never distinguishes itself from the closely overlapping sibling time_convert (or markdown_convert), which the category list 'time' arguably touches.

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 implies usage through the 'omit to get every compatible unit' note and the abbreviation list, but it gives no explicit when-to-use vs alternatives guidance and never explains how to choose this tool over time_convert for time units. Usage is inferable rather than stated.

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