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

With no annotations, the description carries the full burden and does well: it discloses rounding to the cent, date-driven rate lookup with today as default, and — importantly for an agent — the x402 payment cost of $0.005 USDC on Base. It does not cover failure modes (invalid province code, out-of-range date), which keeps it from a 5.

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?

Three sentences, each earning its place: what it returns, how dates drive rates, what it costs. The output shape is front-loaded before the caveats.

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?

There is no output schema, so the description must describe the return — and it does, enumerating the tax components, per-rate and per-amount rounding, and the total. Amounts are stated in CAD. An agent has everything needed to call it and interpret the result.

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%, so baseline is 3. The description confirms province/amount/date usage and adds the 'pre-tax' and 'default today' framing, but adds no format or syntax details beyond what the enum and patterns already specify.

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: computes a Canadian sales tax breakdown (GST/HST/PST/RST/QST) for an amount in a province or territory. Nothing among the siblings (canada_business_days, canada_statutory_holidays, fx_ecb_convert) overlaps, and the description makes the distinction obvious without opening schemas.

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?

Clear context for when to reach for it: any CAD pre-tax amount needing province-level sales tax, with the date parameter used for historical rate changes (Nova Scotia 2025 HST cut). It stops short of explicit when-not guidance or naming an adjacent tool to use instead, but for a narrowly scoped calculator nothing is genuinely ambiguous.

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