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

Annotations already declare this as a safe, deterministic, read-only calculation (readOnlyHint, idempotentHint, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds little beyond that: it enumerates return fields that the output schema already documents, and does not disclose the rate year, whether premiums are capped at max insurable earnings, or rounding behavior.

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 tight sentences, front-loaded with the purpose, followed by return fields and a cross-reference. No filler or hedging.

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 two-parameter calculator with a full output schema and complete annotations, the description covers scope, jurisdiction variants, and the return shape well enough to call it correctly. Minor gaps remain around the applicable tax year and premium caps, which are not stated anywhere in the description.

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 (province enum, gross_annual_cad) are documented in the schema, so the baseline is 3. The description's mention of 'Quebec and non-Quebec residents' loosely maps to the province enum but repeats rather than extends the schema's own explanation of QC vs other rates.

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 ('Calculate Canadian Employment Insurance (EI) premiums') and scopes it to Quebec vs non-Quebec residents, which cleanly distinguishes it from siblings like calculate_canada_rrq, calculate_canada_federal_tax, and calculate_canada_combined_tax.

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 implied by the description's jurisdiction scope, but there is no explicit when-to-use guidance or comparison against the many adjacent Canada payroll/tax siblings. The pointer to list_bundles is a routing hint for related calculators, not a rule for selecting this tool over alternatives.

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