Status now

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

Annotations already declare readOnly/idempotent, yet the description adds substantial behavior beyond them: a one-minute refresh cadence from TfL, the ordering of results (live problems, planned works, good service), and the precise meaning of `stale` including the five-minute threshold and the history-unreadable fallback. That staleness contract is exactly the kind of context an agent needs to decide whether to trust the answer.

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?

Front-loaded with the core purpose, and every clause (ordering, stale definition, disruption payload) contributes information an agent would otherwise have to discover empirically. It is a dense run-on sentence spanning several semicolon-delimited ideas, which slightly hurts scannability but not substance.

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 no output schema, the description must describe the return shape, and it does: status text, worst severity, TfL reasons, good-service boolean, live-vs-planned flag, open disruptions with start times and causes, last poll time, and the stale flag. Nothing an agent needs in order to interpret the response 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 description coverage is 100% and the single `mode` parameter is fully documented with an enum, so the schema carries the load. The description's 'every line' hints at the omitted-mode default but adds no new semantics beyond the schema, which is the expected baseline here.

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 gives a specific verb-and-resource picture: it returns the current status of every line plus open disruptions, the last poll time, and a stale flag. The phrase 'every line' implicitly separates it from the per-line sibling line_status, but no sibling is named explicitly, so an agent must infer the boundary rather than read it.

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?

'Right now' and the stale flag imply this is the snapshot tool to use for present-moment questions, but there is no explicit when-to-use versus line_status, disruptions, or period_stats. The exclusion logic is left to inference.

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