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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description still adds substantial detail beyond them: hard input limits, exact refusal conditions, unit-inference threshold, and the response shape (CSV of input, unit, date plus artifact hash). Nothing about cost or failure modes is left implicit.

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-loaded with the core mapping and constraints, and dense with useful facts. It is slightly repetitive, though: 'The answer is…' appears twice, once for the CSV and once for the JSON envelope, and the full endpoint URL is restated.

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?

A single-parameter tool with no output schema would otherwise leave the return value undefined; the description specifies the CSV columns and the JSON envelope plus artifact hash. Input limits, unit rules and failure behavior are all covered, so an agent can call it correctly without the linked documentation.

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 the baseline is 3; the description earns above baseline by supplying the concrete millisecond threshold (magnitude ≥ 100000000000) that the schema only gestures at with 'whole seconds or milliseconds'. It does not go further into parsing edge cases such as whitespace handling.

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?

Opens with a precise verb+resource+output form: 'Unix timestamps to UTC dates in ISO 8601.' The tool's domain is unmistakable and does not overlap with the arithmetic/encoding/list siblings.

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?

Provides clear operating context — free, one timestamp per line, seconds or milliseconds — and names the conditions under which it refuses input (empty text, >1,048,576 bytes, >10,000 lines, malformed lines). No alternatives are needed given the dissimilar siblings, but there is no explicit statement of when to prefer this over manual conversion or a sibling tool.

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