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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond them: it returns the prices as originally calculated with their date, each insurer's link and the full result link, and explicitly flags that these are historical, not current, prices. It stops short of describing failure behavior for an invalid or unknown reference.

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?

Purpose and identifier format are front-loaded, and the alternative-tool routing closes the paragraph logically. It is a dense single block with several parenthetical asides, slightly heavier than necessary, but no sentence is 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 no output schema, the description carries the return-value burden and does so: it enumerates prices, calculation date, per-insurer links and the full result link. Combined with the staleness warning and the pointer to compare_ctp_prices, an agent has everything needed to call this correctly and interpret the response.

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 coverage is 100%, so the baseline would be 3, but the description earns more by explaining what the reference actually is: an 8-character code shown with a result and at the end of its link (calculator.html?load-result=...). That gives the agent a way to locate or validate the value rather than just its type.

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: 'Open a saved NSW green slip price comparison ... by its Greenslips reference'. It also names the sibling tool (compare_ctp_prices) in the same breath, so an agent can distinguish retrieving a stored result from running a fresh comparison without opening either schema.

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 an explicit trigger ('Use it when someone gives a reference or a result link, to see those prices again, buy or ask about them') and an explicit exclusion with the alternative ('not today's prices: for those, compare again with compare_ctp_prices'). The when/when-not/alternative triad is fully covered.

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