Live vehicle positions

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuine behavioral detail beyond that: stale-vehicle flagging, the typical freshness window, empty-result semantics outside service hours, and the geographic/operator coverage boundary.

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?

Three dense sentences, front-loaded with the core resource and payload, then the staleness caveat, then coverage limits. No filler and nothing repeated from structured fields.

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 usefully names the returned fields (heading, age) and explains the staleness/empty-result semantics an agent needs to interpret output correctly. Coverage limits complete the picture for a no-required-parameter tool.

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%, so the baseline is 3. The description confirms the 'route or line' scoping but adds no syntax, format, or interaction detail beyond what the schema already documents (including the up-to-6 route fan-out).

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?

States a specific verb+resource ('Current GPS positions of OASA vehicles on a route or line') and enumerates the payload fields (heading, report age). It is clearly distinguishable from siblings like stop_arrivals or routes_at_stop, which deal with stops rather than live vehicle telemetry.

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?

Gives real usage conditions: check age_seconds before presenting a position as current, and treat empty results outside service hours as normal. It also scopes applicability geographically (Attica only). It stops short of explicitly naming sibling tools as alternatives for stop-based queries, so it's clear context without full when/when-not routing.

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