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

With no annotations provided, the description carries the full transparency burden. It discloses the cost ($0.005), the data characteristics (source citation, effective date, last-confirmed date, staleness flag), and the authentication/payment options (api_key vs x402). This goes well beyond the schema and is substantive behavioral context.

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?

Two tightly written sentences convey price, purpose, output contents, and authentication details with no filler. The most critical information (cost and what it does) is front-loaded, making it easy for an agent to quickly assess relevance.

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 the absence of an output schema, the description adequately describes what the return value contains (citation, effective dates, staleness flag). It also explains the payment flow. Minor gaps exist around error handling or edge cases, but for a simple lookup tool with clear schemas and examples, it is largely 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?

The input schema provides descriptions for all three parameters (100% coverage), so the baseline is 3. The description repeats the series examples and adds the 'current value' context, but does not add significant new meaning beyond what the schema already states. It meets but does not exceed the baseline.

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 identifies the tool as returning the current value of a reference series, with explicit examples (policy-rate, vat, minimum-wage). It distinguishes itself from siblings like get_series_history (which presumably returns historical values) and list_series (which lists available series). The verb and resource are specific and unambiguous.

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 values, but does not explicitly contrast it with alternatives such as get_series_history for historical data. It provides examples and mentions payment, but no direct when-to-use or when-not-to-use guidance. Usage is inferable but not explicitly stated.

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