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

With no annotations provided, the description carries the burden of behavioral disclosure. It mentions the cost ($0.02) and payment flow via x402, which are key behaviors. However, it does not state whether the tool is read-only or describe any potential side effects like data generation or caching.

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 concise sentences. First sentence states purpose and cost, second explains parameter usage. No wasted words, front-loaded with critical information (cost).

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 tool has one optional parameter and no output schema, the description provides essential context: what it does, cost, and payment handling. It could mention response structure (e.g., 'returns a JSON object keyed by country') but is largely complete for agent invocation.

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 schema covers 100% of parameters (api_key). The description adds value beyond schema by explaining the optionality and payment implications: 'Pass api_key if you have one; otherwise the response explains how to pay via x402.'

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 provides a 'Snapshot of every series for every country in one call', which distinguishes it from sibling tools like get_series or list_series that operate on individual series. The verb 'Snapshot' implies a read operation without modification.

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 indicates when to use this tool (for a global snapshot) and provides payment guidance. However, it does not explicitly state when not to use it or compare with alternatives like get_series for single queries.

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