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

Annotations declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and the description reinforces these with 'READ-ONLY. Does not place orders...'. Additionally, it reveals critical behavioral traits: response caching (~300s), authentication methods (X-Api-Key or x402 payment proof), cost ($0.008 USDC), rate limit (15/min), and the nature of billing as a non-side-effect. This far exceeds what annotations provide.

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 description is somewhat repetitive (the first two sentences restate the same idea) and mixes sections without explicit formatting. While front-loaded with key info, it includes a block of tags that could be trimmed. Each sentence adds value, but the repetition detracts from conciseness. It is adequate but not tightly crafted.

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?

Given the tool's complexity (multiple data sources), full schema, presence of output schema, and annotations, the description covers all necessary aspects: purpose, behavior, authentication, cost, rate limit, caching, guidelines, and output structure mention. It is complete, with no obvious gaps. The rule allowing omission of return value details when output schema exists is satisfied.

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 baseline is 3. The description adds minimal value for the main parameters (symbol and timeframe are self-explanatory). However, it does explain the __x_payment parameter's purpose ('Use when retrying after HTTP 402...'), which is useful context not in the schema. Overall, the description does not significantly enhance understanding beyond the schema.

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 clearly states the verb-resource combination: 'fetch market data' with 'All-in-one market intelligence' listing specific data types (OHLCV candles, indicators, OI, news). It distinguishes from siblings by emphasizing comprehensiveness ('everything an agent needs in one call'), which is unique among many specialized data tools. The redundancy ('Everything...' repeated) is minor and does not obscure clarity.

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 states when to use: 'Compute / parse / backtest only — no live orders.' Provides a concrete integration path: 'Feed outputs into cc.agent_strategy with force_paper=true to paper-trade.' Mentions rate limit and cost as constraints. Lacks explicit when-not-to-use comparisons with siblings, but the guidelines are actionable and contextual.

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