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

Annotations already declare readOnlyHint and idempotentHint, covering safety. The description adds behavioral context by noting that it returns UIC IDs used by other tools and mention of disambiguation between matches. It does not discuss pagination or rate limits, but for a simple lookup, this is sufficient.

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 concise, two sentences, front-loaded with the main purpose, and every sentence adds value. It includes purpose, return format, and usage guidance without fluff.

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 lookup tool with complete annotations and schema coverage, the description fully covers purpose, usage, and return format. It clarifies when it is needed despite search_connections accepting names directly, making it contextually complete.

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 parameters are fully documented in the schema. The description does not add extra semantics beyond the schema; the example UIC ID is about return value, not parameter meaning. Thus, baseline score 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 clearly states the tool's function: 'Search for Swiss train stations, addresses, or points of interest by name.' It also specifies the output (UIC station IDs) and differentiates it from sibling search_connections, making its purpose unambiguous.

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?

Explicit usage guidance is provided: 'search_connections accepts station names directly, so this tool is only needed when the user explicitly asks for station info or when you need disambiguation between multiple matches.' This states when to use and when not to use, naming the alternative.

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