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

Annotations already cover the safety profile (readOnly, closed-world), and the description adds a genuine behavioral fact: omitting `format` returns all 7 styles. It doesn't say what happens when no time input is supplied at all, which is the one behavioral gap for a 0-required-param tool.

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, zero filler, front-loaded with the transformation and an example, then input modes, then the output default. Each sentence earns its place.

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 description resolves the main ambiguity of a six-param, zero-required tool by spelling out the alternative input paths. Minor gap: it never says what a no-argument call does (e.g. defaults to current time or errors), which would fully close the loop.

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 already 100%, so the 3 baseline is met by the schema alone. The description adds value beyond it by explaining that the three input modes are alternatives and by justifying when the date/time/timezone trio is preferable, plus the semantics of omitting `format`.

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 and resource ('Turn a moment in time into Discord timestamp codes') and shows a concrete output example, making it immediately distinguishable from the sibling decode_discord_snowflake. An agent knows exactly what it gets back without opening the schema.

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?

Explicitly names the three mutually exclusive input modes (unix, ISO datetime, or local date+time+timezone) and gives a real-world trigger ('best when the user says e.g. "8pm New York time"'). It also states the omit-format default, so both input and output selection are guided.

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