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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuine value by decomposing the metric (fee + slippage), fixing the notional tiers, and stating the output unit in bps. It doesn't say whether quotes are live or cached, but that is a minor gap given annotation coverage.

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 the metric front-loaded and the unit trailing; every clause (fee, slippage, sizes, direction, venue scope) 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?

For a two-parameter read-only tool with no output schema, the description covers what is computed, at what sizes, and in what units. The only real omission is the meaning of `limit` and the granularity of the returned markets.

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 50%: `venue` is documented in the schema, but `limit` has no description anywhere. 'biggest markets' hints that limit controls how many markets are scanned, yet the description never states it, so it only partially compensates for the undocumented parameter.

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 names a concrete computation (taker fee plus order-book slippage), the scope (one exchange's biggest markets), the sizes ($10k/$100k/$1M), direction (long and short), and the unit (basis points). The 'on one exchange' qualifier separates it from the sibling `execution_cost`, though that sibling is never named explicitly.

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: an agent can infer this is for measuring per-venue round-trip cost, but there is no statement of when to prefer it over `execution_cost` or `best_opportunities`, and no prerequisites or exclusions.

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