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

Substantially exceeds the annotations: it discloses pricing ($0.35), partial-answer refusal semantics (coverage_gap, no_charge), a shared per-IP rate limit, the x402 fallback when no api_key is supplied, the optional Ed25519 receipt behavior, and what is NOT legal advice or a certified extract. This is exactly the auth/rate-limit/failure context annotations cannot carry.

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?

Front-loads the price, which is useful, but the prose is a dense run-on packed with parentheticals, SKU cross-references and pricing caveats that dilute the core purpose. Several clauses (certified-extract pricing, verify_answer_receipt pointer) belong elsewhere.

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-value detail is correctly omitted, and the description covers payment, refusal, coverage and receipt semantics. The one real gap is failing to position the tool relative to the overlapping get_filing_deadlines sibling.

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 86%, so the schema already documents country, tax, from/to, api_key and receipt. The description adds only marginal meaning (card checkout at /pricing, receipt is free but not a certified extract), largely repeating the receipt default that the schema states verbatim. Baseline 3 is appropriate.

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: 'Upcoming VAT, PAYE and corporate-tax due dates in a window', with scope details (default 90 days, weekend/holiday roll, cited rules). However, it never distinguishes itself from the near-identical sibling 'get_filing_deadlines', leaving the agent to guess which to pick.

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?

Gives real operating context – verified coverage limited to AU and NZ, free refusal on coverage gaps, sharing of the 3 free calls per IP per day, and passing api_key vs falling back to x402. But there is no explicit when-to-use/when-not guidance against the many sibling tax tools (e.g. get_filing_deadlines, compute_vat), so selection remains implied.

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