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

With no annotations provided, the description must carry behavioral disclosure. 'Get' implies a read-only lookup and '(Entur)' identifies the data source, which is useful. However, it does not disclose return shape, multiplicity behavior, or error handling for invalid stop IDs.

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?

The description is two sentences with no filler. The primary action is front-loaded, followed by a one-line explanation of why fare zones matter. Every part earns its place.

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 single-parameter lookup, the description plus schema is largely complete: it states the purpose, the required input format, and the source of valid IDs. There is no output schema, so the return representation is left somewhat unspecified, but the description adequately conveys that the result is the stop's fare zone(s).

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 stop_place_id with a pattern, example, and source hint. The description adds domain context but no additional parameter-level semantics beyond what the schema provides.

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 uses a specific verb and resource: 'Get the fare (tariff) zone(s) a stop place belongs to'. It clearly identifies the Entur domain and distinguishes this from sibling departure, accessibility, and quay tools.

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 description gives clear context by explaining that fare zones set the ticket price, which implies when this tool is relevant. The input schema also directs the agent to obtain stop_place_id from resolve_stop_place. It lacks explicit when-not-to-use guidance, but no obvious alternative fare-zone tool exists.

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