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

With no annotations, the description carries full burden and excels. It discloses the paid nature ($0.005), payment workflow via x402, alternative api_key auth, and response attributes (source citation, effective date, last-confirmed date, staleness flag). This goes far beyond a simple read operation and sets clear expectations.

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 two sentences, front-loaded with the cost, and every clause contributes. It packs examples, response content, and payment guidance without redundancy or fluff.

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?

Despite no output schema, the description explains what the response will include (official citation, effective date, last-confirmed date, staleness flag). It covers payment/auth nuances. For a simple current-value lookup, this is complete and self-sufficient.

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 description coverage is 100%, so the baseline is 3. The description adds value by giving series examples and explaining the api_key parameter's role (bypasses x402, metered). It does not add detail for 'country' beyond the schema's enum, but the additional context for series and api_key is meaningful.

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's function: 'Current value of a reference series' with concrete examples (policy-rate, vat, minimum-wage). This distinguishes it from sibling tools like get_series_history (historical values) and list_series (listing series). The verb 'get' is implicit but the resource and scope are explicit.

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 provides clear context for when to use this tool: when you need the current value of a reference series. It implies alternative tools (e.g., historical data would use get_series_history) but does not explicitly name them or state when not to use it. The payment and api_key guidance is helpful context.

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