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 bar is lower. The description usefully adds that results come from the same engine as the official TfNSW planner (authority/quality signal) and describes the shape of a journey (door-to-door, every change, walking legs, departure/arrival times). It does not mention the API-key requirement or any rate limits, though _apiKey is documented in the schema.

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 sentences with no filler; the core purpose is front-loaded in the first clause and the authority/positioning claim is relegated to the second sentence. Every sentence 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 compensates by describing what a returned journey contains (legs, changes, walking, lines, times), and annotations cover the safety profile. It omits the authentication requirement for _apiKey, though that is documented in the schema, so it is nearly but not 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% across all 7 parameters, so the schema already documents origin/destination formats, when, arrive_by, and the type flags. The description's references to departure/arrival times add only marginal semantic value beyond the schema, making the baseline 3 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?

Names a specific verb ('Plan') and resource ('public-transport journey') with an explicit geographic scope ('anywhere in New South Wales') and enumerates the output content (multi-leg, changes, walking legs, lines, times). It does not, however, explicitly distinguish itself from the sibling tfnsw_departures/tfnsw_alerts tools, so it stops short of a 5.

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 line 'AUTHORITATIVE for "how do I get from A to B on Sydney transport"' gives a clear selection condition for this tool. It offers no explicit exclusions or named alternatives (e.g. 'use tfnsw_departures for next real-time departures at a single stop'), so it is clear context without routing away from siblings.

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