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

Annotations already cover the safety profile (readOnly/idempotent/openWorld, non-destructive), so the bar is lower; the description still adds genuinely useful behavior beyond them: it is an official free source requiring no key, and it costs 0.03 USDC per call via x402 on Base. It does not discuss rate limits, latency, or error behavior.

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 core data listing is front-loaded and efficient, but the pricing detail is stated twice ('$0.03 USDC x402 Base' and '[x402: 0.03 USDC per call on Base]'), and the 'SYNTHORA ecb-macro:' brand prefix adds no selection value. Redundancy dilutes an otherwise tight description.

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 single-parameter read-only data fetch, the description covers what data comes back, cost, and auth, which is most of what an agent needs. The gap is the input contract: a caller cannot tell from either the description or the schema what to put in 'input' to get the macro series.

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?

There is a single generic 'input' parameter whose schema text ('product parameters (JSON or text)') is opaque, and the description adds nothing about what that input should contain. With coverage nominally at 100% the baseline is 3, but the schema's content is so uninformative that the description could have compensated and does not.

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 names the specific resource (official eurozone macro from the ECB data warehouse) and enumerates the exact series returned: HICP inflation, MRR policy rate, 10Y govt yield, each with previous value, change and direction. It doesn't explicitly contrast with the nearby sibling ecb_forex_fixing_vs_market, so it falls short of the 5-level sibling differentiation.

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 line 'For macro/rates agents and prediction markets' implies the intended caller but gives no when-to-use/when-not guidance and never names an alternative tool. Usage is implied by audience rather than stated as a condition.

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