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

Annotations cover safety/read-only/idempotent behavior. The description adds that it returns the CRA-listed PST/QST 'for reference' and cites the source table, which is useful provenance. It doesn't note caching/currency beyond 'current', so it's modest added context.

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, front-loaded with the core operation, no filler. Source citation is compact.

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, the return values need not be described. The description covers scope, optional province, and PST/QST reference, but doesn't explain what happens for territories or mixed federal/provincial treatment in enough detail.

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 single parameter is fully described with format examples, so the schema does the heavy lifting. The description's '(or all 13)' does clarify the optional/no-args behavior, which is a slight value add over 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/resource: 'Current GST/HST rate for a Canadian province or territory (or all 13).' It also disambiguates the sibling tools by being clearly the rate-lookup, not the small-supplier check or allowance tools.

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 description implies looking up a rate by province, and 'or all 13' signals the no-arg case. It doesn't explicitly say when to use this versus gst_hst_small_supplier_check, but the purpose is distinct enough that an agent can route correctly.

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