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

No annotations are provided, so the description carries the full burden. It discloses that the tool is PAID ($0.005), that responses include source citation, effective date, last-confirmed date, and staleness flag, and that a later gazette could silently retire the value. It also explains the api_key/x402 payment behavior. This is rich behavioral context beyond the schema.

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 compact and front-loaded with the most critical fact (PAID). Every sentence adds information: cost, examples, response contents, payment path, and follow-up actions. It is slightly dense with parentheticals, but each earns its place.

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 paid, read-only lookup tool with no output schema, the description covers cost, response fields, payment, and follow-up actions. It doesn't describe error cases or rate limits, but the essential operational context is present. The sibling list includes get_series_history, so the agent can infer the difference between current and historical values.

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 schema already documents all three parameters. The description adds examples for series and mentions api_key's role (bypasses x402; metered for invoicing), which adds some value. However, it doesn't add much beyond the schema for country or series format, so baseline 3 is appropriate.

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 specific verb ('get'), a resource ('reference series'), and concrete examples (policy-rate, vat, minimum-wage). It also distinguishes itself from siblings by naming get_changes and register_alert as follow-ups, and the sibling list includes get_series_history and list_series, so the scope is clear.

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 explicitly says when to use this tool: to get the current value of a reference series, and it tells the agent what to do after a 200 (bind get_changes or register_alert). It also explains the payment path (api_key vs x402), which is essential usage context. It doesn't explicitly name alternatives for 'current value vs history', but the follow-up guidance is strong.

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