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

Annotations already cover readOnly/idempotent/non-destructive/openWorld, so the bar is lower, and the description still adds real value: the data comes from a hot cache and is therefore fresher but not authoritative history, plus an explicit auth requirement ('Requires api:read'). It does not describe the shape of the returned 'features'.

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?

One tight paragraph: purpose first, then alternatives, then parameter formats, then auth. Every clause carries information an agent needs; there is no filler.

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 read-only tool with no output schema, the description covers source, freshness, id format, batching, and auth. The remaining gap is that 'market features' is never enumerated, so an agent cannot anticipate what fields come back or whether it should combine this with get_feature for full coverage.

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 50% and the description compensates well: it explains the single-vs-comma-separated batch semantics and pins down the exact id format (bare Hyperliquid symbols like BTC/HYPE, dex-prefixed HIP-3 like xyz:TSLA) plus a cross-reference to scan_markets' `symbol` values. It leaves open the edge case of passing both parameters or neither, which matters since 0 parameters are 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?

States a specific verb+resource ('Real-time market features') with explicit scope (one or more instruments, hot cache) and names the sibling it is fresher than ('get_feature'). An agent can distinguish this from get_feature, get_feature/get_bars, and get_prices 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?

Explicitly routes the agent: use this over get_feature when current conditions are needed, and it explains single-vs-batch invocation. It stops short of a full when-not statement (e.g., historical ranges → get_bars, and what happens if both id params are supplied or neither).

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