last_train_home

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

No annotations are provided, so the description carries the full burden. It discloses that the tool looks at connections departing around 22:00 or after_time, returns the latest one, and includes a human-readable summary. This explains the search window and output format, adding context beyond a minimal description. It doesn't clarify 'realistic' or edge cases, but 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?

The description is two sentences, front-loaded with the main purpose, then usage guidance and behavior. Every clause earns its place with no filler or redundancy.

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?

With an output schema present, return values are specified elsewhere. The description provides sufficient context for selection and invocation: parameters are in schema, and behavior is described. Minor gaps like no-train results are not addressed, but for a simple tool this is adequate.

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?

The input schema provides descriptions for all three parameters, including home_station, current_station, and after_time with format and default. The description adds only a general reference to 'back to home_station' and 'after_time' but no additional syntax or detail beyond the schema, so the baseline of 3 applies.

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 'Find the latest realistic train back to home_station tonight' — a specific verb, resource, and scope. It clearly distinguishes from siblings like get_connections by focusing on the last train home, and from plan_evening_out by its single-query nature.

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 says 'Use this tool when the user asks "when's the last train home from <X>?" or wants reassurance about staying out late.' This gives clear triggering scenarios. It doesn't explicitly name alternatives, but the intent is unambiguous.

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