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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered; the description usefully adds that each list carries active/unsubscribed/cleaned member counts, which is the return shape an agent needs since there is no output schema. It does not mention pagination or account-size limits, leaving a small gap.

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 short sentences with no filler: the first defines the operation and its output, the second gives the follow-up action. Front-loaded with the verb and resource.

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 parameterless, read-only list tool with no output schema, the description covers what is returned and how to use the result, which is most of what an agent needs. The only omission is any note on result size or pagination behavior in large accounts.

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?

The tool takes zero parameters and the description correctly describes none, so there is nothing for it to disambiguate. Baseline for a 0-param tool 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 and resource ('List all mailing lists of the Laposta account') plus the scope of what is returned (member counts). This is plainly distinguishable from laposta_get_list (single list) and laposta_list_members (members of one list) without opening a schema.

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?

'Use the list_id in the other tools' establishes this as the discovery entry point that feeds the rest of the toolset, which is the key when-to-use signal. It stops short of naming exclusions or pointing at laposta_get_list as the single-list alternative, so it is clear context rather than a full routing rule.

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