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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds substantial context beyond them: the api:read auth requirement, the ~850-entry default payload size, and nuanced failure semantics — failed_dexes versus unavailable_symbols vs missing_symbols. That distinction prevents an agent from misinterpreting a transient read failure as a nonexistent symbol.

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 and front-loaded — the scope comes first, then symbol formats, then the guidance to use scan_markets. Every clause carries information, though the single unbroken paragraph packs a lot (pair-id mapping, HIP-3 keys, failure taxonomy) and could be easier to scan.

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?

No output schema exists, so the description compensates by naming the relevant return fields (data.spot_pairs, data.hip3.failed_dexes, unavailable_symbols, missing_symbols). For a one-parameter read tool, nothing an agent needs to call it correctly is missing.

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 100% and already documents the string-or-array form, so the description is not carrying the burden alone. It still adds meaning the schema lacks: which symbol notations are accepted per market type and how spot pairs map back to native HL pair ids via data.spot_pairs.

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 and resource ('Current mid prices') and enumerates the exact asset classes covered: Hyperliquid native perps, spot assets, and HIP-3 builder-DEX perps. It is clearly distinguishable from siblings like scan_markets and search_symbols, which it names explicitly.

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: 'WITHOUT symbols this returns ~850 entries — prefer scan_markets for discovery and pass symbols here for targeted lookups.' It also spells out the acceptable symbol formats (BTC, HYPE/USDC, xyz:TSLA), so the agent knows both when to call it and how.

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