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

Annotations already declare readOnly, idempotent, non-destructive and openWorld=false, so the safety profile needs no restating. The description adds real behavioral context the annotations don't: it returns extension dates, province-specific corporate rules (Quebec/Alberta), and each date's source URL and checked date. It still doesn't say what happens for unsupported entity/jurisdiction combinations.

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, trigger front-loaded before the return-value detail, with no filler. The second sentence is dense with enumerated outputs (federal dates, extensions, provincial rules, source URL, checked date), which is a lot in one breath but every element is relevant.

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 output schema, the description correctly spends its budget describing what comes back – dates, extensions, provincial rules and source provenance. A three-required-parameter tool is well covered; only edge-case behavior (unsupported jurisdiction/entity pairs, fiscal-year entities) is unaddressed.

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% with an entity enum, so the schema already carries most parameter meaning. The description adds mapping value by tying entity types to specific forms (partnership→1065, s_corp→1120-S) and by noting jurisdiction-specific rules, which helps an agent reason about valid combinations.

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 specific verb ('check') and resource ('business tax filing deadlines') and enumerates the exact forms covered (1065, 1120-S, 1120, Schedule C, T2/T1). That enumeration distinguishes it immediately from siblings like estimate_quarterly_tax and get_cra_instalment_dates.

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?

It gives an explicit trigger: 'Call this when a user asks when a business tax return is due.' That covers entity returns and extensions but does not name an alternative or exclusion (e.g., instalment dates belong to get_cra_instalment_dates), leaving the sibling boundary implicit.

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