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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: ~10s recompute cadence during market hours, the funded-API-key requirement with the exact onboarding sequence (create_guest_key → create_credit_checkout → get_credit_balance), the degraded delayed-preview behavior without a key, and a data-only disclaimer. The only gap is return payload shape, which is partly covered by the feature enumeration.

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?

Usage and the alternative are front-loaded, which is good, but the middle is a dense feature dump spanning forecast bands, straddle moves, max pain, session OHLC, order flow, GEX profiles and vanna/charm ladders. Much of that inventory is genuinely informative for a no-schema return, yet the single-paragraph stacking without structure makes it harder to scan than it needs to be.

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?

With no output schema, the description carries the return burden and does so thoroughly: it names the full field inventory, the realtime-vs-delayed modes, the auth path, and the disclaimer. An agent has everything needed to decide whether to call it and what to expect.

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 per the rubric the baseline is 4; there is no parameter semantics to clarify and none is needed.

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?

States a specific verb+resource (fetch current SPX dealer market structure) and enumerates the concrete artifacts returned: walls, gamma flip, net GEX, regime. It explicitly distinguishes itself from the sibling get_regime, so an agent can route without opening schemas.

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?

Opens with the when-to-use condition ('when you need the full current SPX dealer market structure') and names the alternative with a cost tradeoff: 'If you only need the regime label and its confidence, get_regime is smaller and cheaper.' Both the selection condition and the fallback are explicit.

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