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

Annotations already declare read-only, idempotent, open-world and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it is realtime when an API key is supplied and serves a delayed preview without one, which affects freshness expectations. It does not cover rate limits or response payload shape.

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?

Three sentences, each earning its place: the use case first, the routing alternative second, the auth-related freshness caveat last. No filler or restated name/title.

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?

There is no output schema, and the description compensates by naming what is returned (regime label plus confidence). Usage routing and the API-key freshness caveat round it out, though it stops short of describing the label vocabulary or confidence scale.

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 takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool applies. The schema's additionalProperties=false is consistent with the description implying a no-argument call.

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 names a specific resource (SPX dealer regime label) plus its confidence value, and explicitly distinguishes itself from get_market_structure, which covers walls, gamma flip, net GEX and strike detail. An agent can tell it apart from siblings like get_regime_segments without opening any schema.

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?

It states the exact condition for use ('when you only need the current SPX dealer regime label and its confidence, for example to check whether conditions have changed') and names the alternative tool to use for richer structure output. Both the when and the when-not are explicit.

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