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

Annotations already declare this as read-only and idempotent, so the description doesn't need to repeat safety traits. Beyond annotations, the description reveals that the tool returns UIC station IDs and can search addresses and POIs, adding valuable behavioral context about output and coverage. It doesn't mention ordering or pagination, but that's not critical for a simple read-only search 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?

The description is two sentences, front-loaded with the core purpose and followed by a practical usage note. Every sentence earns its place with no redundancy or fluff, making it appropriately sized and well-structured.

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?

The description fully covers the tool's scope, output (UIC IDs), and usage context, including when it should not be used. Given the simple schema and rich annotations, no additional information is necessary for an agent to correctly select and invoke the tool.

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 coverage is 100%, with both query and limit having descriptions in the schema. The description does not add additional parameter-level detail beyond the schema; it only mentions 'by name' which aligns with the query parameter. Since the schema already explains parameters, the description provides minimal extra semantic value, so a baseline 3 is appropriate.

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 clearly states the tool's function: 'Search for Swiss train stations, addresses, or points of interest by name.' It specifies a concrete action and resource. It also distinguishes from the sibling tool search_connections by noting that search_connections accepts station names directly, making this tool's unique purpose (station info, disambiguation) 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 description provides explicit usage guidance: 'this tool is only needed when the user explicitly asks for station info or when you need disambiguation between multiple matches.' It also names the alternative (search_connections) and when to use it instead, giving clear context for tool selection.

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