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

Goes well past the annotations (readOnlyHint/openWorldHint) with real behavioral facts: 0.5% fee is embedded in the swap, the service is non-custodial and never sees keys, sanctioned wallets are refused, EVM returns an exact-amount approval first when needed, and Solana returns one base64 versioned transaction the wallet pays for. That is exactly the context an agent needs before surfacing transactions to a user.

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?

Front-loaded with the action and chains, then the return shape, then per-chain mechanics — a sensible order. The closing "xStocks are coming soon" is marketing that does not help invocation and is the one sentence not earning its place.

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?

There is no output schema, and the description compensates fully by describing the return: a firm quote with amount out, minimum, and every fee, plus unsigned transactions in order. Combined with the per-chain transaction shapes and the fee/custody notes, an agent has everything needed to call it and explain the result.

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%, including the default-chain note and the 'same forms as sell' reuse for buy, so the schema already does the heavy lifting. The description adds no parameter-level detail beyond it (no clarification of slippage behavior, amount precision, or address format), so 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 — "Build a swap" — and adds the crucial scope "for your own wallet to sign and send," plus the exact artifact returned (firm quote + unsigned transactions in order). It never names swap_quote, so the boundary with that sibling is left to be inferred from "to sign and send" rather than stated outright.

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 implied by "for your own wallet to sign and send" and the per-chain breakdown, which tells an agent this is the self-custody execution path. There are no explicit when-not conditions and no named alternative (e.g. swap_quote for preview-only pricing), so the agent must infer the routing.

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