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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering safety. The description adds meaningful behavioral context: it discloses the realtime vs delayed preview distinction and the API key requirement, which are not in annotations. It also clarifies the response is limited to label and confidence, setting expectations about data scope.

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?

Two sentences with no fluff. The core purpose is front-loaded, and the authentication caveat is a single additional clause. Every word earns its place.

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 simple zero-parameter read-only tool, the description covers the essential: what it returns, the realtime condition, and the auth requirement. It lacks an explicit description of the output format (e.g., does 'confidence' mean a number 0-100 or a string?), but since there is no output schema, the description could be slightly more explicit. However, given the simplicity and the annotations covering safety, it is adequately complete.

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 tool has zero parameters, so the schema is trivially complete. Baseline for no parameters is 4. The description does not need to explain parameters since there are none. It adds no param info but none is required.

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 resource (SPX dealer regime), the exact data returned (label + confidence), and the scoping qualifier 'current' and 'only'. This clearly distinguishes it from sibling tools like get_regime_segments, which likely returns more detailed regime data, and get_market_structure, which covers a different concept.

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 explains the realtime vs delayed preview behavior based on API key presence, which is context about authentication and freshness. However, it does not explicitly guide the agent on when to choose this tool over alternatives like get_regime_segments or get_market_structure. The 'label + confidence only' hint implies it is for a quick summary, but no direct comparison or exclusion is given.

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