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

With no annotations, the description carries the full behavioral burden and does well: it discloses that the call is paid ($0.005 USDC on Base or Solana), needs no account or API key, is not charged on failure, and names the underlying endpoint. Remaining gaps are return shape/latency and whether repeat calls or caching affect cost.

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 purpose is front-loaded in the first clause, followed by fields, then cost/auth terms, then the endpoint URL — a sensible priority order with no filler. The lone redundancy is 'Paid.' preceding a sentence that already states the exact price.

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?

For a zero-parameter, no-output-schema purchase tool, the description supplies what an agent needs: the exact metrics returned, their provenance, the price, accepted chains, the no-charge-on-failure policy, and the URL. It stops short of describing response structure or freshness date, which matters somewhat since no output schema exists.

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?

The tool takes zero parameters, so the baseline is 4; there is no argument surface for the description to clarify. The description correctly spends its words on the returned metrics instead of inventing parameter detail.

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?

The description states a concrete verb and dataset: 'Economic data for country CA' with an explicit field list (GDP, growth, inflation, unemployment, population, GDP per capita) and a named source (World Bank). The country code in the name and text separates it from the ~50 buy_econ_* siblings, though it never explicitly routes to buy_econ_us or buy_fx_cad for adjacent needs.

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?

Usage is implied rather than stated: it is clearly the Canadian macro-data endpoint, and pricing/auth terms tell the agent what to expect. There is no explicit when-to-use guidance, no exclusion of alternatives such as buy_fx_cad for CAD exchange rates, and no note on data staleness or refresh cadence beyond 'latest World Bank values'.

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