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

Annotations already declare this a safe, read-only, idempotent, closed-world computation, so the safety bar is low. The description goes beyond that by enumerating the four outputs produced (must-register determination, cessation timing, effective registration date, next-quarter headroom) and the scope boundary on entity type. It does not mention edge-case behavior, but for a deterministic calculation this is adequate.

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 action and immediately followed by the concrete outputs and the scope caveat. Dense but every clause carries information; the parenthetical naming the two tests is slightly heavy but justified.

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?

An output schema exists, so return values need not be spelled out, yet the description still summarizes them helpfully. Annotations cover the safety profile, and the description covers the tests applied, the input domain, and the entity-type limitation. Nothing material for correct invocation is missing.

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% and both parameters carry their own descriptions, including the definition of taxable revenue and the quarter numbering. The description adds conceptual framing ('taxable revenue by calendar quarter') but no syntax or format detail beyond the schema, so the baseline 3 applies.

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 operation (apply the CRA's $30,000 small-supplier tests), the exact inputs it operates on (taxable revenue by calendar quarter), and the precise outputs (registration requirement, cessation date, effective registration date, headroom). This is clearly distinguishable from the sibling tools, which are rate lookups and allowance calculators.

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 establishes clear context (determining GST/HST registration status via the two small-supplier tests) and an explicit exclusion — charities and public service bodies are out of scope. It doesn't name sibling tools or conditions for choosing between them, but none of the siblings overlap functionally, so the gap is minor.

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