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

With no annotations, the description carries the full burden and does well: it discloses the metered price ($0.002 USDC per call), the payment mechanism (x402 on Base) which implies wallet/auth prerequisites, and the data provenance with a fallback source. It omits error behavior for unsupported symbols/intervals and any rate-limit or caching behavior.

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?

Two tight sentences: the first front-loads capability, fields, and sourcing; the second front-loads the cost and payment requirement. Nothing is wasted and no sentence merely restates the tool name.

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 3-parameter tool with no annotations and no output schema, the description covers data source, field-level return contents, granularity, and payment cost, which is most of what an agent needs. The remaining gap is failure modes (unknown ticker, unavailable exchange) and the exact response shape beyond field names.

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 by establishing that symbol is the base asset quoted against USDT and summarizing the interval range and candle cap. It does not clarify the oddity that limit is typed as a string or how invalid values are rejected.

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: spot OHLCV candles for a coin against USDT, with sources (Binance with OKX fallback) and returned fields (open/high/low/close, change %, VWAP). The granularity clearly separates it from prices_token_price and prices_movers, though it never names a sibling 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?

Usage is implied by the detail (interval range, 1000-candle cap, Binance-then-OKX sourcing), but there is no explicit 'use this when' guidance or mention of when to prefer prices_token_price instead. The agent must infer the selection criteria from the resource description.

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