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

Annotations already declare readOnly, openWorld, and idempotent hints, so the description doesn't need to restate safety. It adds valuable context beyond annotations by stating it is keyless (no auth required) and describing the return fields (stop id, coordinates, country).

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?

Three sentences, no filler, with purpose front-loaded, return information in the middle, and usage guidance at the end. Every sentence earns its place and the routing advice is concise despite covering multiple siblings.

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 2-parameter search tool with full schema coverage and safety annotations, the description covers what the tool does, what it returns, when to use it, and keyless access. Nothing needed to invoke it correctly is missing.

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 clear descriptions for both 'query' and 'results'. The description adds examples and contextual usage but does not materially extend the parameter meaning beyond the schema, so the baseline of 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 uses a specific verb ('Search') and clearly defines the resource: German/European rail stations, stops, and places by name. It also distinguishes itself from siblings by stating that other dbrail tools accept plain names and that this tool is for disambiguation or coordinates.

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?

It explicitly tells the agent when this tool is unnecessary ('You do NOT have to call this first'), when to use it instead ('disambiguate between similarly-named stations or need coordinates'), and names the sibling tools that can resolve names directly. This leaves no ambiguity about tool selection.

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