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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, covering safety. The description adds valuable behavioral context: it explains the output includes operational statuses (Good Service, Minor Delays, etc.), reason for disruption, severity score (0-10), and counts. It also notes no auth is required and cites the data source. This goes beyond the annotations by describing what the response contains and the data licensing, though it does not mention rate limits or pagination, which are minor for a read-only tool.

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 dense paragraph but is well-structured: it starts with the core purpose, then details the output, parameter options, use cases, and source/auth. Every sentence adds useful information without redundancy. It is longer than typical but justified by the breadth of functionality; no fluff or filler. It earns a 4 for being efficiently packed.

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 complete for an agent to call this tool correctly. It covers what the tool does, what it returns (statuses, reasons, severity scores, counts), the parameters and their defaults, use cases, the data source, and authentication requirements. With an output schema present and 3 optional parameters, the description covers all necessary context, leaving no ambiguity about when or how to invoke it.

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%, with each parameter (modes, detail, include_good_service) fully documented in the schema. The description repeats these meanings and adds default behavior (e.g., default modes) but does not add meaning beyond the schema. Since the schema already documents everything, the description provides reinforcement but no new information, fitting the baseline 3.

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 it retrieves real-time service status for all TfL lines, enumerates the transport modes covered, and distinguishes it from sibling tools like arrivals, bike points, and journey planning by focusing on network-wide line status rather than specific stops, bike availability, or routes. The verb 'Get real-time service status' is specific and the resource (all TfL lines) is explicit.

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 states it is useful for journey planning, commuter alerts, and real-time London transport monitoring, which gives context. It does not explicitly name sibling tools or state when NOT to use it, but the focus on line status versus arrivals or journey planning is clear from the content. The distinction is implicit but adequate for an agent to select it for overall network status queries.

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