Market Regime Context

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

Beyond the readOnly/idempotent/destructive annotations, the description explains the fail-closed backwardation rule, the leakage-safe as-of semantics, the 1-2 day substrate lag, and the constancy of values per scan_date. This gives the agent a clear behavioral model without contradicting the 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 front-loaded with the core purpose, then structured into rail explanation, data freshness caveat, args, and returns. Every sentence adds substantive value; no filler or repetition.

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 single optional parameter and an output schema, the description covers the return shape, parameter semantics, safety interpretation, and data lag. An agent has enough to call the tool correctly and interpret its result without further documentation.

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 input schema only provides a nullable string with a default of null, but the description compensates fully by specifying the YYYY-MM-DD format and the default behavior (latest scan date carrying regime features). For a single optional parameter, this is complete.

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 identifies the tool's resource and purpose: point-in-time market-regime context for a scan date, including VIX, VIX3M, SPY trend, VIX delta, and the regime safety rail. It does not explicitly differentiate from the listed siblings, but its domain is distinct enough that an agent can infer what it provides.

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 implied use case is retrieving regime features for a scan date, and the description gives helpful caveats about substrate lag and leakage-safety. However, it does not explicitly state when to choose this tool over siblings or when not to use it.

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