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

Annotations only declare readOnlyHint=true; the description carries the rest and does so richly — provider fallback chains per market, the auto-fallback heuristic, hard-constraint error behavior for spot/perp, and that the response labels the market/interval/source actually delivered and flags a still-forming last candle. This is exactly the behavioral context annotations cannot express.

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?

A single dense paragraph that front-loads purpose before parameters, with no filler sentences. It is long and unsegmented, so the nested auto-fallback rule is harder to scan than it could be, but every clause carries information.

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?

An output schema exists, so return format need not be explained, yet the description still notes response labeling, USD volume presence, and the forming-candle flag. Combined with the parameter semantics, an agent has everything needed to call it correctly.

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%, so the baseline is 3, but the description adds real meaning beyond the schema: the provider chain behind each 'market' value, the auto-fallback condition, and the error-not-substitute contract. Some redundancy exists (it restates the interval enum list, limit default/max, and days deprecation already in the schema), which keeps it from a 5.

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?

Opens with a specific verb+resource ('OHLC(V) candle history for a coin by symbol') and immediately scopes it with the key identifying parameters. An agent can distinguish this from siblings like market_history, market_quotes, or ta_technicals without opening 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?

Gives strong in-tool selection guidance: 'market' spot/perp/auto with an explicit preference order and the exact condition under which auto falls back to perp (spot history shorter than the request and than 210 candles), plus the fact that spot/perp are hard constraints that error rather than substitute. It does not, however, say when to reach for this tool instead of sibling tools such as ta_technicals or market_history.

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