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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered structurally. The description goes beyond that by defining what counts as 'taken' (all company busy events plus the caller's own busy time) and where working hours come from (booking settings or a 09:00-18:00 / 60-minute default), which is genuinely useful behavioral context. It stops short of covering timezone handling, pagination, or what happens when service and duration_minutes conflict.

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?

The core scope is front-loaded in the first clause, followed by usage and then behavioral detail in descending priority. Em dashes and parentheticals pack a lot of meaning into roughly five sentences with no filler.

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 no output schema, the description correctly compensates by naming two return fields (hours.configured and the ready-to-use 'text' line). For a three-parameter read tool this is close to complete, with only the service/duration interaction and timezone assumptions left unstated.

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 only 33% — only 'date' is documented in the schema — so the description has to carry weight, and it does: it states the date format and today-default, explains that a company-defined service length is used when available, and implies the 60-minute default for visit duration. The duration_minutes parameter itself is never mentioned by name, so the mapping from that parameter to the stated default is left implicit.

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?

The description uses a specific verb+resource ('Free appointment windows of the caller's company on one local day') and defines the scope tightly to a single day. It is clear what the tool returns, but it never names the closest siblings (planner_suggest_slots, planner_get_availability), so differentiation relies on the agent inferring it from the description alone.

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?

It gives concrete triggering contexts — answering a query like 'вільні вікна на завтра' and checking availability before booking a client — which covers the main when-to-use cases. There are no explicit exclusions or pointers to the alternative tools an agent might reach for instead, so the routing guidance is incomplete.

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