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

Annotations already declare readOnly/idempotent/non-destructive, so the description's job is to add what they can't: the $0.01 USDC-on-Base payment model, the fact that a 404 for uncovered ids incurs no charge, and that every figure is cited to the statistics office. The no-charge-on-miss detail is exactly the kind of cost/safety behavior an agent needs before spending.

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?

Four tight sentences with no filler, and cost is front-loaded so an agent sees the price before the capability. Minor redundancy: the id enumeration repeats the schema enum almost verbatim, costing a little space for little new information.

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 shape need not be described. The description covers price, coverage boundary, failure mode, and the free alternative — everything an agent needs to call this correctly and safely.

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% and the enum already constrains id to US/UK/EA/JP, so the description's id list is partly redundant. It still adds real semantics by stating that non-listed ids yield 404 rather than an error charge, which the schema does not convey.

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 ('latest inflation (CPI or HICP) print for a covered country or area') and enumerates the payload (headline, core, selected categories, each cited to the statistics office). It also distinguishes itself from the free sibling sample_macro, so an agent can route without opening either schema.

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 an explicit when-to-use ('Call when you need the latest inflation print'), names the free alternative for the US case (sample_macro id CPI), and states the supported id set plus the consequence for unsupported ids (404, no charge). Both the selection condition and the fallback are spelled out.

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