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

Annotations only declare readOnlyHint=true, so the description carries the rest, and it does add real context beyond that: the exact set of searchable fields, the pagination workflow ('pass next_page as page'), the response content ('contact data and totals'), and the underlying endpoint. It does not cover ordering/sorting behavior beyond the direction param, but the additions are meaningful for a read-only list 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 short, front-loaded sentences that lead with what is listed before drilling into search fields and pagination. The trailing 'GET /clients/index.json' is marginal filler since the schema already carries the parameters, but nothing is padded or buried.

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?

For a read-only, zero-required-param list tool with a fully documented schema and no output schema, the description covers purpose, filter semantics, and the pagination loop an agent must follow. It stops short of describing result shape or default sort field, but the essential call-correctly information is present.

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%, so the schema already documents all six parameters (page, search, per_page, direction, created_period, modified_period) including their enums and defaults; baseline is 3. The description's enumeration of searchable fields adds a little precision over the schema's vaguer 'names, numbers, e-mails ...', but the pagination hint largely restates what the page parameter description already says.

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 ('List the address book (clients and suppliers)') and clarifies that the resource spans both clients and suppliers, which is useful scoping. It implicitly separates itself from the singular superfaktura_get_client and the create variants via the 'list' verb, but never names an alternative, so sibling differentiation is inferential rather than explicit.

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 mention that 'search matches name, IČO, DIČ...' implies when to supply the search parameter, and the pagination note implies when to use page/next_page, giving usable implied guidance. However, there is no explicit when-to-use or when-not-to-use statement, and no reference to the single-record superfaktura_get_client alternative for looking up one client.

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