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

Annotations already declare readOnlyHint=true, and the description adds valuable behavioral context: the calculation methodology (FRED M2 YoY growth, M2 velocity z-scores, 36-month trailing window), monthly update cadence, and historical coverage since 1962. It also notes the Gold tier requirement for the history parameter via schema, but the description itself mentions the data source and composite structure.

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 (two sentences plus an update note) while packing essential details: output fields, methodology, data source, usage triggers, and update frequency. No filler or redundant phrasing.

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?

Since there is no output schema, the description compensates by listing all return fields (score, trend, monetary_impulse_label, m2_yoy_pct, etc.) and explaining the data source and scope. It fully equips an agent to decide when to invoke this tool, though it could add interpretation of the 0-100 score, which is not necessary for selection.

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 100% for the single optional 'days' parameter, which already explains the history behavior and Gold tier requirement. The description adds no additional parameter semantics beyond what the schema provides, so baseline 3 is appropriate.

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 states a specific verb ('Returns') and a well-defined resource: a 0-100 money-supply momentum index composed of FRED M2 YoY growth and M2 velocity z-scores. It enumerates the exact output fields (score, trend, etc.), making the tool's purpose unambiguous and distinct from generic siblings.

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?

Explicitly specifies when to call: 'when the user asks about M2 money supply growth, liquidity, money velocity, or monetary tightening/easing regimes, or when timing duration positioning...' This provides clear usage context, though it lacks exclusions or named alternative tools.

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