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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description goes further by disclosing the units convention, that negative fees are rebates, and what artifacts come back (results, conditions, assumptions, editable link, share page, PNG) — meaningful behavior beyond the annotations.

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?

Two dense sentences with zero filler: the cost model is front-loaded, then output artifacts and the safety boundary. Every clause carries information.

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 an output schema present and annotations covering the safety profile, the description need not explain returns or permissions; it supplies units, sign conventions and the no-execution caveat. Adequate, though it omits any mention of error conditions or input validity limits.

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 all five parameters, including defaults and ranges. The description adds the 1 bp = 0.01% conversion and restates that negative fees are rebates, marginal extra value over the per-parameter docs.

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 phrase 'Round-trip spread economics' names a specific domain and the three modeled cost components (spread, fee, adverse), which distinguishes it from siblings like trade_expectancy and compound_interest. It is clear but never explicitly contrasts itself with those alternatives.

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?

Usage is only implied by the cost-model framing; there is no statement of when to pick this over position_size or trade_expectancy. The closing boundary 'No account access or order execution' usefully scopes it out of live-trading territory, which partially compensates.

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