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

No read-only or destructive annotations are provided, so the description carries the behavioral disclosure burden. It does state the output will include affected lines and reasons, but it does not disclose behavior when there are no disruptions, data freshness, or whether omitting 'modes' returns all lines or none.

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 a single, front-loaded sentence that directly states the tool's purpose and scope. Every word contributes value, with no filler or redundant repetition of the tool name.

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 tool with one optional parameter and no output schema, the description adequately covers purpose, location, and result content. However, it leaves gaps about default behavior when 'modes' is omitted and the response format for a healthy/no-disruption state, which would be useful for an agent to fully understand outcomes.

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 schema already describes the single 'modes' parameter fully, including accepted values (tube, dlr, overground, elizabeth-line, tram) and comma-separated format. With 100% schema coverage, the description adds no additional parameter-level meaning beyond the London-only scope.

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 phrase ('Which lines are delayed... right now') and clearly identifies the resource as live transit disruption status in London. It distinguishes itself from sibling tools like transit_arrivals and transit_nearby by focusing on delays/suspensions/closures rather than arrivals or nearby stations.

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 clear context: it is for current disruption status in London only. However, it does not explicitly mention alternative tools for other transit queries (e.g., arrivals) or say when not to use this tool, so usage guidance is mostly implicit.

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