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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety bar is low; the description still adds real value by naming the upstream source (CRA's 'Charge and collect the GST/HST' table) and the as-of/effective-from dates, which tells the agent how fresh and authoritative the numbers are. It marks the PST/QST figure as CRA's reference value, a meaningful caveat.

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 tight sentences, front-loaded with the resource and scope, followed by provenance and return shape. The enumeration of returned fields overlaps with what the output schema already conveys, which is the only wasted effort.

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?

For a single-parameter read tool with an output schema, the description covers scope, provenance, and data currency, which is what an agent needs to trust and call it. Minor omissions are how province names/codes are matched and that the PST/QST figure is informational only for provinces without HST.

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% and the lone parameter is already documented with examples, so the baseline would be 3. The description goes one step further by clarifying the omission behavior — no province yields all 13 rows — which the schema does not state.

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 names the exact resource (current GST/HST rate per province/territory, all 13 or one) and adds the PST/QST reference value, so the agent knows precisely what data comes back. It doesn't explicitly separate itself from the nearby 'ontario_hst_basics' or 'gst_hst_small_supplier_check' siblings, leaving that differentiation to inference from the province scope.

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?

Usage is only implied: the '(or all 13)' phrasing hints that omitting a province returns the full table, but there is no explicit statement of when to call this versus the Ontario-specific or small-supplier siblings. No exclusions or prerequisites are given.

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