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

The description adds substantial context annotations do not: the exact price ($0.01 per call), the settlement rail (USDC on Solana via x402), and the concrete MCP handshake (call without payment → PaymentRequired challenge → retry with payment at _meta["x402/payment"]). That is genuinely operationally useful. It does not clarify what the series looks like (default period count, ordering, units), which is the remaining gap.

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 sentences, front-loaded with what the tool returns, then the payment protocol. Efficient, though the parenthetical payment retry instructions are dense and the HTTP line is somewhat redundant given the MCP path is already spelled out.

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 data-fetch tool with no output schema, the definition covers access mechanics well but leaves the return payload unexplained – no description of series length, ordering, units, or what a 'normalised' value means, and no default stated for the optional 'periods' parameter. Adequate but incomplete.

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 'country', 'indicator' (with its enumerated ids), and 'periods' are already fully documented in the schema. The description only adds the 30-country scope, which is marginal beyond the schema. Baseline 3 applies.

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?

States the resource specifically: 'Normalised indicator series for 30 countries', which tells an agent what data comes back and the geographic scope. It does not differentiate itself from nearby siblings like stats_trade, macro_cpi, or macro_unemployment, so an agent must still infer which is the right source for a given indicator.

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?

There is no guidance on when to use this tool versus macro_cpi/macro_unemployment/macro_cpi or stats_trade, nor prerequisites beyond payment mechanics. The only 'how' present is the x402 payment retry procedure, which is protocol mechanics rather than task routing guidance.

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