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

Goes well beyond the readOnly/idempotent/openWorld annotations: exact price ($0.35), the no_charge refusal contract for partial coverage, the shared free-call quota, what the optional receipt does and does not represent, and the legal-advice disclaimer. An agent knows cost, failure mode, and side effects before calling.

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?

Pricing and purpose are front-loaded in the first sentence, and every later sentence carries load-bearing information (coverage, refusals, quota, receipt). The dense parenthetical style is heavier than ideal but wastes little.

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 an output schema present, return values need not be described, and the annotations plus description together cover pricing, refusal behavior, rate limits, receipt provenance, and verification path. Nothing an agent needs in order to decide and invoke 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 coverage is already high (86%), so the baseline is 3, and the description adds real meaning on top: the default 90-day window behavior, receipt semantics (Ed25519 answer receipt only on paid success, no charge), and api_key's bypass of x402 with metering. It stops short of explaining year_end or the tax enum beyond enumerating the three taxes.

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 date window, with holiday/weekend rolling and cited rules. The scope is clear and the verified-country list (AE, BH, OM, QA, SA) matches the country enum. It does not, however, differentiate itself from the near-twin sibling get_filing_deadlines, leaving ambiguity about which to choose.

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 clear operating context: default 90-day window, shared 3-free-calls-per-IP-per-day allowance, pass api_key or get an x402 payment requirement, and free refusal on coverage gaps. It also rules out confusion with the certified-extract SKU. It never says explicitly when to prefer this over get_filing_deadlines, so no true exclusions are stated.

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