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

With no annotations, the description carries the full burden. It discloses the cost ($0.005), the need for api_key or x402 payment, and the response metadata (source citation, effective date, last-confirmed date, staleness flag). This goes beyond basic purpose and gives important behavioral details, though it omits potential rate limits or error behavior.

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 description is three sentences with no wasted words. It front-loads the cost and purpose, then adds return metadata and authentication details. Every sentence earns its place, making it highly efficient.

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?

Given there is no output schema, the description explains what each value contains. It covers cost, purpose, authentication, and response metadata. It does not detail response structure or potential errors, but for a simple getter with moderate complexity, this is reasonably complete.

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. The description adds value by providing concrete examples for the 'series' parameter (policy-rate, vat, minimum-wage) and clarifies the role of api_key in bypassing x402 payment. It also implies that country is needed but relies on the schema for exact enum values.

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 clearly states the tool returns the current value of a reference series, with examples like policy-rate, vat, and minimum-wage. It implicitly distinguishes from siblings like get_series_history (by using 'current') and list_series, but does not explicitly name alternatives, so it falls short of a perfect score.

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?

The description implies usage for retrieving current reference series values and mentions payment/authentication, but it does not explicitly state when to use this tool versus alternatives such as get_series_history or list_series. There is no 'when not to use' guidance, so usage context is only implied.

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