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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds pricing, the free-refusal path (coverage_gap, no_charge), the shared rate limit, the payment flow, and receipt semantics. This is unusually rich behavioral disclosure for a read-only tool and materially de-risks an unexpected charge.

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?

The payload is front-loaded well ('PAID ($0.25). Country evidence pack...'), but it reads as a single dense run-on with a long parenthetical and repeats the receipt-vs-certified-extract distinction that the schema already states. Every fact is relevant, yet the packaging is not tight.

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 not required, and the description covers payment, refusal, defaults, rate limits, and verification path (verify_answer_receipt against /certified/public-key). An agent has enough to call this correctly and anticipate cost outcomes.

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% so the baseline is 3, but the description adds meaning the schema lacks: what happens when series is omitted (default first certifiable of vat/policy-rate/minimum-wage) and the constraint that all named series must be certifiable. It also restates the receipt caveat, which the schema already covers.

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 resource and composition: 'the full cited country brief plus up to 3 Ed25519-signed certified extracts.' It also gives the default series set (vat, policy-rate, minimum-wage), which lets an agent distinguish this bundle from get_country_brief and from the non-MCP certified-extract endpoint.

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 usage context — it is paid ($0.25), requires certifiable series, shares 3 free calls/IP/day with the answer tools, and returns an x402 payment requirement without an api_key. However, it never explicitly says when to prefer this over siblings like get_country_brief or get_series, so routing is left to inference.

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