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

Beyond the annotations it discloses substantial behavior: exact price ($0.25), the shared 3-free-calls-per-IP-per-day quota, the free-refusal path (coverage_gap, no_charge), the auth model (api_key vs x402), and that receipt=true adds an Ed25519 answer receipt at no extra cost only on paid success. It also notes the tool is not legal advice.

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?

One dense paragraph, front-loaded with price and purpose, and every clause carries operational information. There is some duplication with the schema (receipt semantics restated) and the parenthetical asides make it heavy, but nothing is filler.

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 values need not be described; the description covers the payment, refusal, quota, auth, and verification (verify_answer_receipt against /certified/public-key) aspects an agent needs to call and interpret it correctly.

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 100%, but the description adds real meaning: series must all be certifiable and default to the first certifiable of vat/policy-rate/minimum-wage; receipt semantics (unpaid 402 and free refusals exclude one). This goes beyond the schema's per-field descriptions.

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+resource: a paid 'Country evidence pack' containing the full cited country brief plus up to 3 Ed25519-signed certified extracts. It explicitly distinguishes itself from the free brief, from the $0.10 /v1/certified SKU (noting that SKU is not an MCP tool), and from the answer tools it shares quota with, so an agent can place it relative to siblings.

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 conditions: named series must all be certifiable, otherwise refused free with coverage_gap/no_charge; pass api_key if you have one, else the result is the x402 payment requirement. It does not explicitly route the agent to a free alternative (e.g. get_country_brief or get_series) for non-paid needs, so it stops short of full when/when-not guidance.

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