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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful operational context beyond annotations: the upstream is free, a server-side key is required, and the tool covers roughly 800k series across major data sources. It does not describe response format or pagination, but this is less critical given the rich annotations.

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 description is compact, front-loaded with the core action, and every sentence earns its place. The examples are inline and the coverage/key-requirement details are relevant operational context. There is no fluff or repetition of schema information.

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 tool with no output schema, the description could say more about the response structure, units, or default time range. However, the name and 'time-series' wording make the return type clear enough, and the description covers input alternatives, scale of data, source coverage, and the server-side key requirement. It is adequate for correct invocation, with only minor gaps around output details.

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 description significantly enriches the main parameter series_or_slug by listing many example slugs and clarifying the raw-ID alternative. However, schema description coverage is only 60%; sort and limit have no description in the schema and the tool description does not explain their semantics either. The main parameter is well handled, but 40% of the schema is left without added meaning.

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 opens with a specific action and resource — 'Fetch any FRED time-series' — and clearly scopes the tool to retrieval via curated slug or raw FRED ID. Concrete examples ('gdp', 'CPIAUCSL') make the operation unambiguous and distinguish it from sibling tools like fred_search and fred_popular, which are about discovery rather than direct series fetching.

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 implies the right usage — call this tool when you already have a slug or raw FRED series ID — but it does not explicitly say when to prefer fred_search or fred_popular instead. There is clear context on input forms, but no direct when-to-use/when-not-to-use routing.

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