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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds that it is 'plain-language' with 'CRA sources', which signals a curated static reference, but says nothing about staleness, jurisdiction limits, or how the facts are presented beyond the annotation coverage.

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?

A single front-loaded sentence with zero filler; the covered topics are listed compactly and the sourcing note is appended efficiently.

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 parameters and an output schema present, the description needn't explain return values, and it enumerates the substantive topics a caller would expect. The only gap is not routing the agent between this reference and the more specific sibling tools.

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?

Zero parameters and 100% schema coverage, so there is nothing for the description to disambiguate. Baseline 4 applies for a parameterless tool.

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 a clear resource ('plain-language basics for Ontario businesses') and enumerates the exact topics covered: 13% HST rate, $30,000 threshold, 29-day deadline, place-of-supply rule. That enumeration partly differentiates it from siblings like gst_hst_rate_by_province and gst_hst_small_supplier_check, though it never explicitly positions itself against them.

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?

There is no statement of when to use this tool versus the sibling rate/supplier tools, nor any exclusions. The agent must infer that this is a general reference while the siblings perform specific lookups or checks, which is not spelled out.

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