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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds the meaningful behavioral constraint that the tool works only for business days, which is not present in the annotations. It does not explain what happens for non-business days (e.g., whether it returns null or errors), but this extra context goes beyond structured metadata.

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 two concise sentences with no redundant words. The main output is front-loaded, followed by key constraints. Every word earns its place, and the structure is ideal for quick parsing.

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?

Given the tool's simple interface, a rich output schema, and strong annotations, the description is nearly complete. It covers what the tool does, the date format, and the business-day limitation. The only missing piece is explicit guidance on fallback behavior for non-business days, but that is a minor gap given the output schema likely covers error handling or null values.

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 schema already documents both parameters thoroughly (series_id enum with descriptions, date pattern with example), so the baseline is 3. The description adds semantic value by emphasizing 'Business days only' and reiterating the YYYY-MM-DD format, which reinforces date handling expectations. This extra contextual guidance warrants a 4.

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 uses a specific verb ('Returns') and clearly identifies the resource ('the value of any supported FRED series for a specific date'). This distinguishes it from sibling tools like get_current_value (which lacks date specification) and get_treasury_yield_by_date (which is narrower in scope).

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 clearly conveys when to use this tool: when you need a historical value for a supported FRED series on a specific date. It adds the constraint 'Business days only' and a date format reminder, but it does not explicitly mention alternatives or exclusions, such as pointing to get_current_value for live data. This is clear context without explicit alternative references.

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