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

Annotations only cover readOnlyHint and openWorldHint, so the description's disclosure that each call costs $0.002 USDC via x402 is genuinely additive and important for an agent deciding whether to call it. It also adds the 300-bar cap and the fact that change/high/low come back per period, but says nothing about rate limits or failure 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?

A single dense sentence with no filler; the resource is front-loaded and the cost caveat closes it. It is long but every clause (pairs, intervals, bar cap, return fields, price) carries information an agent needs.

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?

With no output schema, the description still conveys the shape of the return (OHLCV plus change, high, low for the period) and the critical cost/payment model. For a 3-parameter read-only market-data tool, an agent has enough to call it correctly; only pagination/default specifics are 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 only 33% (only interval is described in-schema), so the description must compensate and largely does: it defines pair as a Coinbase pair with format examples, bounds limit at 'up to 300 bars', and restates the interval enumerations. Only the default for pair/limit and whether limit is required remain unaddressed.

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?

Names a specific verb+resource (OHLCV candles), scopes it to Coinbase pairs with concrete examples (BTC-USD, ETH-USDC, SOL-USD), and enumerates the supported intervals and 300-bar cap. It is unambiguous against generic siblings like crypto_price or chart, though it never explicitly names the alternative to use instead.

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 description implies usage (historical bars for a pair) but never states when to pick this over crypto_price, token_chart, crypto_indicators or crypto_orderbook. No exclusions, prerequisites, or routing guidance are offered despite many overlapping crypto siblings.

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