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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the tool is known to be non-mutating. The description goes well beyond this: it reveals that the unsigned transaction commits the user to nothing, explains the approval requirement and the exact sequence (submit approval, wait, then submit originalTransaction), and clarifies that 'recipient' is only for relaying. It also exposes the dependency of unit on action. This is rich behavioral disclosure with no contradictions.

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?

The description is compact yet dense, with every sentence adding distinct value. It leads with the key constraint ('v3 only') and the core operation, then methodically covers the crucial edge cases (units, asAToken, recipient, approval flow). No fluff or repetition of schema fields; it's an ideal length for an agent to parse quickly.

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?

Given the tool's complexity (8 params, 5 required, no output schema), the description covers all critical aspects an agent needs to call it correctly: version restriction, non-custodial nature, unit semantics, approval handling, and even hints at the response shape (ApprovalRequired, approval, originalTransaction). There's no missing information that would cause an agent to mis-invoke the tool.

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?

Although schema coverage is 100% (all parameters have descriptions), the tool description adds substantial semantic meaning: it clarifies the ambiguous 'amount' by tying it to action type (assets vs shares), explains the effect of asAToken (skips supplying when wallet holds aToken), and states that omitting recipient defaults to sender. This elevates the parameter understanding beyond 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?

The description clearly states the tool's purpose: 'v3 only. Build an unsigned transaction to move value in or out of an Aave Vault.' It identifies the specific resource (Aave Vault), the verb (build), and the exact set of actions (deposit, mint, withdraw, redeem). This distinguishes it from sibling prepare_* tools like prepare_order or prepare_liquidation, which operate on different instruments.

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 provides strong usage context: it's v3 only, non-custodial (so the agent should proceed without asking), and explains the unit handling (assets vs shares) and asAToken behavior. It also describes the approval flow when needed. However, it does not explicitly name alternative tools or state when to use this instead of them, though the abundance of other prepare_* siblings makes that somewhat implicit.

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