Plan a rail journey

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

With no annotations provided, the description carries the behavioral burden. It clearly discloses the multi-step orchestration: finding trains, checking availability and fares for preferred classes, and ranking options. It does not mention failure modes, execution time, or the fact that it does not create bookings, but the core behavior is transparent.

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 sentences with no waste: the first defines what the tool does, and the second gives clear usage guidance. The key information is front-loaded, and every sentence 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?

The description is adequate for a high-level one-shot planner: it explains purpose, main inputs, and ranking behavior, while the schema covers all 8 parameters in detail. However, with no output schema and no description of the returned ranked options, error cases, or edge conditions, it has clear gaps that could affect an agent's confidence in interpreting results.

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 all parameters, defaults, constraints, and enums. The description adds only marginal conceptual context, such as 'preferred classes' and 'ranks the options', but does not need to compensate for missing parameter documentation.

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 states a specific verb and resource: it is a one-shot journey planner that finds trains, checks availability and fares, and ranks options. It also distinguishes itself from sibling tools by explicitly saying it replaces chaining the individual tools, so an agent can clearly tell it apart.

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 explicitly tells the agent when to use this tool: 'Use this instead of chaining the individual tools when the user asks how to get from A to B.' This clearly communicates the condition and points to the alternative approach, leaving no ambiguity about when the tool is appropriate.

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