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

Annotation readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds the API endpoint and the shape of the returned payload, which is useful, but says nothing about auth requirements, not-found/error behavior, or whether results are cached/filtered.

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 compact fragments that front-load the returned data before the endpoint detail; no filler. It could drop the raw endpoint with no loss, but overall it is tight and well-ordered.

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 single-parameter read tool with annotations covering safety and no output schema, the description does the right thing by enumerating the returned fields. Error/not-found handling is the only meaningful omission.

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% and the single client_id parameter is fully documented (including its type and that it comes from superfaktura_list_clients). The description adds no parameter meaning beyond the schema, so 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?

States a specific verb+resource ('Get a client') and enumerates the returned fields (address, tax ids, bank data, currency/due days/discount, statistics), which is more than a restatement of the title. The singular 'client' vs the sibling 'superfaktura_list_clients' implies single-fetch versus list, but the description never explicitly contrasts them, so sibling differentiation is left implicit.

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?

Usage is implied: fetching one client by id, where the id originates from the list tool (noted only in the schema, not the description). There is no explicit when-to-use, when-not-to-use, or alternative routing, though in a get/list family the context is reasonably clear.

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