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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, and the description goes well beyond them: auth methods (X-Api-Key or x402 proof with HTTP 402 on anonymous calls), a per-call cost of $0.005 USDC, a 30/min rate limit, standard tier, live/near-real-time data, and an explicit 'billing, not a side effect' clarification. These are exactly the operational traits an agent needs and cannot get from annotations alone.

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?

The body is organized into labeled sections (Purpose, Behavior, Auth, Cost, Rate limit, Tier, Returns, Guidelines, Tags), which aids scanning. However, the entire 'Purpose' sentence is duplicated verbatim in the opening sentence and again after 'Purpose:', wasting a substantial block of tokens, and the indicator list is long enough to obscure the core instruction.

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 values need not be explained, yet the description still summarizes them (values, signals, divergences, crossovers per data point). Combined with auth, cost, rate limits and the paper-trading handoff, the definition covers everything needed to invoke the tool correctly; only sibling disambiguation is thin.

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 description coverage is 100%, so the baseline is 3; the schema already documents bars, action, overlays, indicators, candles and __x_payment. The description adds only marginal meaning (default 100 bars, use 300 for overlay-consistent lookback, same code the chart draws), which is useful but largely restates the schema's enum/option lists.

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?

The description names a concrete verb and resource — computing 25+ named technical indicators (SMA, EMA, RSI, MACD, ATR, Bollinger, Ichimoku, VWAP, etc.) on any OHLCV data, plus Smart Overlays via action=smart_overlays. That is specific enough to distinguish it from data-fetching siblings like cc.auto_fetch_market_data or cc.ma_fetch. It does not, however, contrast itself against the potentially overlapping cc.indicator_generator or cc.strategy_data_parser, so the boundary with those siblings is left implicit.

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?

The Guidelines block states the scope of use ('Compute / parse / backtest only — no live orders') and names the intended downstream step ('Feed outputs into cc.agent_strategy with force_paper=true to paper-trade'), which is actionable routing guidance. It also notes the 300-bar recommendation for smart_overlays. It stops short of explicit when-not-to-use or which sibling to prefer for raw market data, so it is clear context without full exclusion rules.

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