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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds that results are informational metadata (city, country, network zone) about where servers can run, which is useful context, but says nothing about result volume, stability, or rate limits.

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 zero waste: the resource and its returned fields are front-loaded, and the API mapping trails as supplementary detail.

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 simple read-only list tool with no output schema, annotations covering the safety profile, and full parameter coverage, the description does enough: it identifies the resource and the fields returned, compensating for the absent output schema. Only the usage guidance is genuinely thin.

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% (the single 'name' parameter is documented as a filter with an example, fsn1), so the schema carries parameter semantics. The description adds no further meaning beyond noting that locations are where servers run, which is the expected baseline when the schema does the heavy lifting.

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 (List) and resource (datacentre locations), and even names the fields returned (city, country, network zone) plus the underlying API route. An agent can tell it apart from read/write siblings like hetzner_get_server, though the 'list vs get' distinction is left to naming conventions rather than stated explicitly.

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?

There is no when-to-use guidance, no mention of related reference-data siblings (hetzner_list_server_types, hetzner_get_pricing), and no indication of when the optional name filter is worth using. The agent gets no help choosing this tool over alternatives.

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