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

Annotations already declare readOnly, idempotent, and non-destructive hints, so the description does not need to re-litigate safety. It adds meaningful context beyond those hints by stating the required FRED_API_KEY environment variable, the data source, and the response format of date/value pairs plus series metadata. Rate limits and error behavior are not mentioned, but this is a read-only data fetch with solid annotation coverage.

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 well structured with a lead sentence, a bulleted use-case list, parameter hints, and an environment requirement. It is slightly longer than necessary because the four bullets overlap in meaning, but every section adds useful operational context.

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?

The description gives the important operational details: what data to expect, when to use the tool, which parameters matter most, and the API key requirement. However, it does not address the limit default, the max observation count, the odd mix of unrelated schema parameters, or possible failure modes. Since an output schema is available, the return-value gap is reduced, but the schema's confusing parameter surface leaves some ambiguity.

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 reported as 0%, so the description must carry the burden of explaining parameters, but it only mentions observation_start, observation_nd, and frequency. It does not clarify the limit parameter, date-format expectations, or the large set of fin-specific fields present in the schema such as wholesaler_ids, exclude_filers, source_resource_id, and optional_additional_filters. The description covers the core FRED parameters but leaves many schema fields unexplained.

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 clearly states a specific action and resource: 'Fetch time-series observation data from FRED for a specific economic series.' It distinguishes itself from the sibling tool SearchFredSeries by explicitly instructing agents to use SearchFredSeries first when the series ID is unknown. The return shape is also previewed, which makes the tool's purpose immediately unambiguous.

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 provides an explicit 'Use this tool when' list covering macro data, advisor/fund context, time-period comparisons, and current indicator values. It also gives a clear conditional routing instruction: use SearchFredSeries first if the series ID is unknown. This is sufficient guidance for an agent to decide when to invoke this tool versus the main sibling.

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