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

Annotations already mark it read-only and open-world, and the description adds meaningful behavior: 'value' is the latest non-null observation with 'prev' being the one before it, partial failures degrade to 'notes' rather than failing the whole snapshot, and missing FRED_API_KEY surfaces a hint. This is more than the annotations alone provide.

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 dense but well-organized into Args, Returns, Examples, and Errors, with the core purpose front-loaded. Every section contributes operational knowledge rather than restating the name or schema.

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 one-parameter, read-only snapshot tool with an output schema, the description is complete: it defines the return shape, explains degraded behavior, names the alternative for historical/flexible queries, and covers the API-key prerequisite. Nothing essential is missing.

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 100% and the single set parameter already has an enum and default, so the baseline is 3; the description adds real value by itemizing exactly which indicators each set contains and clarifying transformations such as CPI YoY %. This makes choosing the correct set much easier.

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 verb and resource: 'Fetch a predefined set of key US macro indicators from FRED in one call' and enumerates exact series by set. It clearly distinguishes this snapshot tool from get_fred_series by emphasizing predefinition and single-call behavior.

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?

It provides explicit selection guidance: 'Don't use for historical analysis or non-listed series — use get_fred_series instead,' plus natural-language examples that map to set values. This tells an agent exactly when to invoke this tool versus its closest sibling.

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