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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered and the description correctly does not contradict it. The description adds only a summary of the payload shape, which is already captured by the existing output schema, and says nothing about timezone handling, historical accuracy, or edge-year behavior.

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?

One front-loaded sentence with no filler, and the default behavior is placed early. The phrasing 'the dates, which way and at what time' is slightly informal but still parses cleanly as a list of outputs.

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 annotations covering safety and an output schema covering return values, the description only needs to establish purpose and scope, which it does well. The only residual gap is the unmentioned lang parameter, though the schema documents it adequately.

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 50%: lang is fully documented in the schema while year carries only min/max bounds. The description compensates partially by explaining that year defaults to the current year, but it never mentions the lang parameter or its pl default, leaving that entirely to the schema.

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 (clock changes) with a defined geographic scope (Poland) and enumerates exactly what is returned: dates, direction of change, time, and the next change from today. None of the sibling tools (sun_times, solstice, moon_phases, find_city) overlap with this domain, so an agent can route unambiguously.

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 parenthetical 'this year by default' tells the agent the default behavior when no year is supplied, which is useful invocation guidance. However, there is no explicit when-not guidance and no mention of any alternative tool, so usage is only implied.

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