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

Annotations only declare readOnlyHint=true, but the description adds genuinely useful behavior: the call is metered at $0.004 via x402 and resolved through a specific GET endpoint, and the payload is limited to summary statistics rather than raw chain data. It doesn't cover response latency, failure modes, or what happens on unpaid requests, which keeps it below 5.

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 tight sentences, no filler, and the metric list is compact. The pricing and URL lead the description, which is slightly awkward front-loading of a commercial detail ahead of the functional purpose, though the content itself 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 one-parameter, read-only lookup with no output schema, the description covers the returned fields, the cost, and the scope limit, which is nearly everything an agent needs. Missing only access/payment mechanics (how x402 settlement is actually performed) and any error behavior.

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% and there is a single required parameter already documented as "US equity or ETF ticker" with a validating pattern. The description adds no format or constraint detail beyond that, so the baseline 3 applies.

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?

"Options activity summary" plus a concrete enumeration (upside/downside lean, volume and open-interest ratios, max pain, largest OI strikes, median IV) tells an agent exactly what the tool returns. The trailing "Summary stats only" carves out a scope limit. It stops short of naming how it differs from siblings like levels or brief, so a 4 rather than 5.

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?

Usage is only implied: an agent infers this is the options-activity product for a ticker. No when-to-use vs when-not guidance, and none of the sibling tools (brief, levels, regime, setup, trend) are referenced as alternatives. The "Summary stats only" phrasing hints at a boundary but doesn't say what to use instead for a full chain.

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