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

Beyond the readOnly/idempotent/non-destructive annotations, it discloses no auth required, a 60 req/min rate limit, single non-paginated response, the meaning of mfos_count: 0, and the data-model caveat that MFOs attach to regions so all cities in a region share a company list, plus Kyiv's is_city: true special case. These are behavioral traits annotations cannot express.

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?

Purpose is front-loaded and most sentences carry distinct information, but the block is dense and the citation instruction ('При використанні посилайтеся на canonical_url') plus the data-source credit are lower-value padding for tool selection.

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 fully specifies the return shape, pagination behavior, rate limits, and the edge-case semantics of mfos_count: 0, giving an agent everything needed to call and interpret it correctly.

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 description coverage is 100% for the single lang parameter, so the schema already carries the enum semantics. The description adds no further meaning about lang (e.g., which surfaces the language affects), so the baseline 3 applies.

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 gives a specific verb+resource ('Перелік областей України та міста Київ') and enumerates the exact fields returned per region (name, city count, MFO count, canonical_url, markdown_url). It explicitly contrasts itself with siblings, stating the city list is not here but comes from get_city without the city parameter.

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 states concrete use cases ('щоб знайти slug області для get_city або для параметра region у search_offers, чи щоб відповісти, у яких регіонах є пропозиції') and names the alternative tool plus the condition that routes to it. The exclusion ('переліку міст тут немає') removes the most likely mis-selection.

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