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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely important context beyond that: per-call cost ($0.003 USDC via x402), the ranking order, and that copyrighted series are flagged as unservable. It omits rate limits and how the limit parameter affects result volume.

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?

A single tight sentence that front-loads the action and scope, then the return fields, with cost last. Every clause carries information, though the colon-delimited field list makes it dense to parse in one pass.

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, the description usefully enumerates the returned fields and adds the copyright/servability caveat plus the pricing model, which is exactly the kind of thing an agent needs before invoking a paid endpoint. It still leaves limit semantics and the follow-up retrieval path unstated.

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 coverage is 50% — 'q' is described as 'Keywords' but 'limit' has no description anywhere. The description's 'by keywords' and 'most popular first' roughly map to these two parameters but add no syntax, default, or maximum for limit, so the undocumented half stays undocumented.

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 a specific verb ('Search') and resource ('FRED economic series'), plus the scope (800,000+) and ranking behavior ('most popular first'). It also enumerates the fields returned, so an agent knows exactly what it gets back. It stops short of naming the sibling it complements (fred_series), so sibling differentiation is only implied.

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?

Usage is implied by 'Search ... by keywords' — you call it when you have keywords and need to discover a series — but there is no explicit when-to-use, no exclusions, and no pointer to the retrieval sibling (fred_series) for pulling actual observations. Adequate but with clear gaps.

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