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

The description asserts 'Read-only, instant, no money moves', but the annotations declare readOnlyHint=false. This is a direct contradiction: the agent is told the operation is read-only while structured metadata says it is not. Although the fee/Sharpe-path disclosure is otherwise rich, the contradiction with annotations dominates this dimension.

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?

Purpose is front-loaded and the sentences carry real information (fee mechanics, gross-path caveat, live fee comparison). However, the trading-cost explanation is largely duplicated in the include_fees parameter description, which is some redundancy in an otherwise dense, useful block.

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?

No output schema exists, and the description compensates by naming the return contents (total return, Sharpe, max drawdown, number of points). It also covers the api_key requirement, crypto-only limitation, and instant/no-capital-movement behavior, so an agent has what it needs 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 description coverage is 100%, so the schema already documents api_key, period_days, constituents, include_fees, and starting_capital. The description adds the interpretation of the fee model (gross vs net path, Sharpe/drawdown unaffected) but largely restates what the include_fees parameter description already says, so the baseline 3 applies.

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 ('Backtest an event-card IDEA — an arbitrary basket of crypto assets — over historical prices') and explicitly distinguishes it from card creation with 'WITHOUT creating a card'. An agent can differentiate it from siblings like build_custom_event_card, preview_card_basket, and trade_event_card without opening any 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 clear context: use this to test a basket of crypto assets before/without building a card, and notes the api_key prerequisite with its source ('register_agent, no key needed'). It does not name a specific alternative tool (e.g., preview_card_basket or build_custom_event_card) as the 'instead use X' case, so 5 is not warranted.

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