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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering the safety profile. The description adds valuable context by listing the returned data fields and the source of valid vehicle IDs, which helps the agent understand the tool's scope and data provenance. It does not contradict annotations and provides reasonable behavioral detail beyond the structured fields.

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: purpose, usage context, and explicit exclusion. Every sentence earns its place, and the most critical information (what it returns and when to use) is front-loaded. 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?

For a single-parameter lookup tool with full schema coverage, explicit output schema, and strong annotations, the description covers purpose, usage, data source, and alternatives. It is fully complete for an agent to select and invoke the tool correctly without needing additional context.

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 for the single parameter is 100%, with the schema already explaining vehicle_id as 'Vehicle ID as returned by get_route_realtime, get_nearby_vehicles, or get_stop_realtime.' The description repeats this source information rather than adding new meaning, so it earns 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 opens with a specific verb ('Returns full details') and resource ('specific transit vehicle by its ID'), enumerating the exact data fields (position, bearing, route, license plate, direction, upcoming stop arrivals). It clearly distinguishes this tool from siblings like get_route_realtime by emphasizing 'specific vehicle' and explicitly naming the alternative for route-wide queries.

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?

Provides explicit use case ('when the user wants to track a particular vehicle'), a concrete example (after seeing it on a get_route_realtime map), source tools for vehicle IDs, and a direct exclusion with the correct alternative tool ('Do NOT use this to get all vehicles on a route — use get_route_realtime instead'). This is model-level usage guidance.

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