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

Goes well beyond the readOnly/openWorld annotations: discloses per-call pricing ($0.005 USDC), the failure mode (fewer than two venues answering) and that it is not charged in that case, the fee assumption (entry-tier taker fees unless overridden), and the scope exclusion of transfer/withdrawal costs. These are exactly the traits an agent needs before spending money on 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?

Dense but well front-loaded: purpose first, then outputs, then cost/failure caveats. It is one long run-on construction and 'Read-only: places no order' mildly repeats the annotation, keeping it from a 5.

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 carries the return-value burden and does so fully (per-venue bid/ask/mid, average fill, ranked routes with net proceeds), plus error and billing behavior. Nothing essential is missing for correct invocation.

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 100% so the baseline is 3; the description adds real meaning by explaining that takerFeesBps overrides the default entry-tier fee on both legs and that sizeUsd drives the 'average fill' calculation. That clarifies defaults and intent beyond the schema text.

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 ('cross-exchange spot price spread') and names the exact asset universe, venues, and outputs (bid/ask/mid, average fill, ranked net-of-fee routes). This clearly separates it from siblings like crypto_price, token_price, order_book_aggregator, and swap_quote.

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 makes the use case evident (finding cross-venue arbitrage routes net of fees) and names exclusions ('transfer and withdrawal costs aren't included') plus a prerequisite (at least two exchanges must respond). It stops short of naming competing sibling tools to redirect to, so it's clear context without explicit alternatives.

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