singapore_get_bus_arrivals

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

Annotations already cover read-only, idempotent, open-world and non-destructive. The description adds value beyond them: this is live/real-time data (not cached historical), an API key is required, and a data-format pitfall (leading zeros) is flagged. It still omits freshness/update cadence and any rate-limit behavior.

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?

Two short sentences, front-loaded with the capability, then the prerequisite and the format caveat. No filler.

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 an output schema present, return values needn't be described, and the description covers the essentials: what data, auth requirement, and a format gotcha. The main remaining gap is the unmentioned service_no parameter and the lack of any note on data freshness.

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 0%, so the description must carry parameter meaning, and it only partly does. 'Bus stop codes retain leading zeros' usefully explains the bus_stop_code format pitfall, but the optional service_no filter is never mentioned, leaving an agent to guess what it does.

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 states a specific resource and result set: live next-bus arrivals (ETA, load, accessibility) at a given bus stop. It is distinguishable from singapore_find_nearby_bus_stops by implication, though it never names the sibling to make the split 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?

'Requires LTA_ACCOUNT_KEY' gives a real prerequisite for invocation. However, there is no statement of when to use this versus singapore_find_nearby_bus_stops (to resolve a stop code first) or the other LTA/carpark/taxi tools, so routing must be inferred.

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