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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description needn't restate them. It adds genuine value by disclosing that the data is live and carries a freshness signal ("when the count was last updated"), which tells the agent staleness is knowable. It does not mention rate limits or the API-key requirement beyond what the schema states.

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 tight sentences with no filler: the resource and return fields are front-loaded, then the authoritative-use statement and enumeration hint. Every clause earns its place.

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, and with no required params the zero-arg and one-arg modes are both covered. Minor omissions (rate limits, whether the key must be supplied on every call) keep it from being fully complete.

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% and both parameters are fully documented in the schema, including the omit-to-list-all behavior and the API key source. The description's "call with no id to list every facility" largely restates the facility_id schema text, so it adds little beyond the baseline.

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 and resource — live occupancy at TfNSW commuter car parks — and enumerates the returned fields (spaces total, spaces taken, last-updated timestamp). It is clearly distinguishable from the other tfnsw_* siblings (alerts, departures, trip_plan), which cover different data.

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?

"AUTHORITATIVE for 'is there parking left at my park-and-ride station'" gives a concrete when-to-use trigger, and "call with no id to list every facility" covers the enumeration case. It stops short of naming explicit exclusions or alternative tools, so it is clear context without full when-not guidance.

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