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

Annotations already cover safety (readOnly, non-destructive, openWorld), and the description adds substantial extra context: free/public, no API key required, ~60s refresh cadence, and the exact row fields returned. This is well beyond the annotation baseline.

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?

Front-loaded with the core purpose, then usage chain, then field/refresh details. Slightly dense with three trailing sentences, but each carries distinct information (fields, refresh, coinId guidance), so little is wasted.

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 two-optional-param discovery tool with an output schema and read-only annotations, the description covers purpose, usage chain, auth/availability, freshness, and the returned identity fields. Nothing needed to invoke 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% with both parameters fully described (limit 1-100 default 20, direction enum gainers/losers), so the schema does the heavy lifting. The description mentions gainers/losers and ordering but adds no format or default detail beyond the schema, so 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?

States a specific verb+resource (scan tracked crypto universe for biggest 24h moves) with scope: top gainers or losers ordered by change percent. It clearly positions itself as a discovery tool distinct from siblings like get_candles and get_market_context, which it names.

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 says when to use it ('DISCOVER candidates beyond your watchlist') and which tools to chain afterward (get_candles, get_market_context, get_news) before trading. It even gives a when-not-style warning: do NOT re-resolve coinId from symbol.

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