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

Annotations cover readOnly and openWorld, but the description adds material context the annotations cannot: every call is charged in USDC, charges are bounded by wallet/budget caps, and the returned data is third-party content rather than instructions (an explicit prompt-injection warning). Gaps remain on rate limits and failure/refund 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?

Front-loading is good — payment terms and the third-party-data warning come first, followed by the product table. However, the description is visibly truncated mid-sentence ('for one currency (e.g.' and 'Federal Reserve Bank of St.'), which is a structural defect that leaves the reference material incomplete.

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?

With no output schema and a nested open-ended params object, the description correctly carries the burden of naming products, prices, and per-product parameters, which it does. But the truncated product entries prevent an agent from fully understanding the two products' scope and semantics, leaving the definition partially adequate.

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 already 100%, so baseline is 3, but the description adds value the flat schema cannot express: it maps each product to its own required params (pair*/currency* for macro.ecb.fx, seriesId*/id* for macro.fred.series) and notes EUR base for FX. Value is undercut by the truncated product lines.

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 opening sentence names a specific resource domain — 'Economic time series (FRED) and ECB reference exchange rates' — and the product list gives concrete product ids with prices. It is distinguishable from most siblings, though the near-duplicate relationship with call_product/list_products is not addressed, and the product lines are truncated mid-sentence.

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 explains the payment model (USDC per call, budget caps) but gives no when-to-use guidance relative to alternatives such as call_product or list_products, which appear functionally overlapping. No prerequisites, no exclusions, no routing logic.

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