Today's date in the user's timezone

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

With no annotations, the description carries the full burden, and it does disclose two useful behavioral facts: the exact return tuple and the cross-tool invariant that every Cozi result also carries this timestamp (which bounds how often it must be called). It does not explicitly state that the tool is side-effect-free or discuss timezone/DST edge cases, so it falls short of a 5.

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?

Two tight sentences, front-loaded with what it returns and followed by the one condition that governs when to call it. Every clause earns its place; nothing is repeated from the title or schema.

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?

There is no output schema, but the description enumerates the returned fields ({date, weekday, time, timezone}) and explains the one non-obvious interaction (other Cozi results already carry the time). For a zero-param, read-only context tool this is 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline of 4 applies. The description appropriately spends no words on parameters.

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 resource (current date, weekday, time on the user's machine) with an explicit return shape, and its identity is unambiguous against calendar/list siblings that mutate data. An agent can tell at a glance that this is a clock/context tool, not a data access tool.

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?

Gives an explicit trigger ('call it before turning "tomorrow" or "this Saturday" into ISO dates') and an explicit exclusion ('when you have not called another Cozi tool yet; every Cozi tool result also carries this time'). This is exactly the when/when-not guidance that prevents redundant calls.

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