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

Goes well beyond the readOnly/idempotent/openWorld annotations: discloses the ≤15s cache, that data comes from the venue tape and is never a curated list, that delisted names are dropped, and that quality flips to 'degraded' when a failed refresh serves the last good snapshot. That last detail is exactly the freshness caveat an agent needs.

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?

Dense but front-loaded: the resource and ranking lead, followed by fields, authority claim, and freshness caveats. Slightly run-on in places, but almost every clause carries a distinct fact with little waste.

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?

Output schema covers return shape, and the description still layers on the non-obvious semantics (freshness, degradation, legality of symbols, cost). For a one-param listing tool, an agent has everything needed to call it and interpret the result.

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 coverage is 0% for the single 'limit' param, so the description must compensate. It supplies the meaningful default ('top 50 by default') but never explains the maximum of 200 or how ranking interacts with limit, leaving half the parameter semantics undocumented.

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 resource (live perps universe ranked by 24h notional volume) and enumerates the returned fields. The line 'THIS IS THE AUTHORITY on which symbols exist' sharply differentiates it from sibling tools that merely consume symbols, so an agent can pick it without inspecting the 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 implies the use case via 'an asset is legal exactly when it appears here', which tells the agent to consult it for symbol validity, but it never explicitly names an alternative (e.g. market_state, feed) or states when *not* to call it. Usage is inferable rather than spelled out.

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