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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds non-obvious facts annotations cannot carry: a $0.05 USDC charge per call via x402 on Base mainnet, fee and slippage modeling, H1/H2 out-of-sample split, a 'luck flag', and a survivorship-bias-free universe. Cost and payment-rail disclosure is exactly the kind of behavioral context an agent needs before committing to a call.

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?

Three compact sentences; capability and bias-free claim come first, the free pre-check pointer last, with no filler. Minor crowding comes from compressing strategy names, cost, and output features into one sentence, but nothing is genuinely redundant.

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 complex nested-payload backtester with no output schema, the description should say what comes back (metrics, equity curve, trade list) and clarify the universe modes that materially change results; it only gestures at H1/H2 and the luck flag. The core capability and cost are covered, but the agent is under-informed about outputs and the universe option.

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?

At 63% schema description coverage the schema does much of the work, and the description reinforces the strategy-type axis and the fee/slippage realism. It says nothing about the universe object (point_in_time vs current_top), the start/end window, initial_capital, or include_trades, leaving those to the schema alone.

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 any crypto strategy') and enumerates the four strategy families (breakout, momentum, dip-buy, MA trend) that map to the discriminated union in the schema, so an agent can recognize what work is done here. It does not explicitly contrast with optimize_strategy, the sibling most likely to be confused with it, so it falls short of full sibling differentiation.

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?

'Free pre-check: validate_backtest' is a concrete routing instruction and is the single most useful usage signal for an agent deciding between the paid tool and its validator. There is no statement of when NOT to use this tool (e.g. versus optimize_strategy for parameter search), so guidance is helpful but incomplete.

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