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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the agent knows this is a safe read. The description adds useful context beyond annotations by detailing the contents (e.g., 'ordered stop lists', 'route polylines', 'workday and weekend schedules are included in each stop's schedule field'). While it doesn't mention error cases or network behavior, the static read-only nature is well disclosed and non-contradictory.

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 three sentences that flow logically: first states what is returned, then defines when to use, and finally states exclusions and prerequisites. Every sentence contributes value with no filler or redundancy. It is front-loaded with the core purpose.

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?

Given the output schema exists (covering return values), the description fully covers the tool's purpose, usage context, parameter meaning, and relationship to sibling tools. It addresses the main use cases and explicitly points to alternatives where relevant. The tool is simple (one parameter) and the description is complete for an AI agent to select and invoke it correctly.

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 coverage is 100% with a clear parameter description ('Route short name (e.g. "T30", "32A") or numeric external ID.'). The tool description repeats this and adds a discovery hint, but that hint is more of a usage guideline than new parameter semantics. Since the schema already covers the parameter completely, the baseline of 3 is appropriate.

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 opens with a specific verb and resource: 'Returns static route metadata: short and long name, vehicle type, brand colour, ordered stop lists for both directions, and route polylines (shapes) for map rendering.' This precisely defines the tool's output and clearly distinguishes it from sibling tools like get_route_realtime, which is explicitly named as the alternative for live positions.

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 explicit when-to-use guidance: 'Use when the user asks which stops a route serves, what a route looks like on a map, or what the scheduled departure times are.' It also gives a clear exclusion: 'Do NOT use this when live vehicle positions are needed — use get_route_realtime instead.' Additionally, it offers a discovery fallback: 'call get_stops_around_location first if you only know a location.' This is exemplary usage guidance.

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