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

Despite readOnlyHint already covering the safety profile, the description adds substantial context: about half the USDC is swapped to WETH in the same transaction, USDC approval is bundled when needed, the output is unsigned transactions to sign in order plus an EIP-5792 batch and a sign_url, simulated from the wallet, and 'Nothing is sent.' This is exactly the non-obvious behavior an agent needs.

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 paragraph with the action front-loaded and no filler; each clause carries information. It is close to optimal, though the transaction/return details could be slightly more scannable.

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 itself and does so: it explains the unsigned transactions, the EIP-5792 batch, the sign_url, the simulation, and that nothing is broadcast. For a build_* tool with an already complete input schema, nothing an agent needs to invoke it correctly is missing.

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 all five parameters are already documented, and the baseline is 3. The description does explain the two deposit modes (which maps to amount_usdc alone vs amount_usdc + amount_weth) and gives minimum thresholds, but it says nothing about auto_compound or the vault default, adding only marginal meaning beyond the schema.

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 states a specific verb and resource: 'Open a new position in an automated vault with USDC... or with both WETH and USDC.' Combined with the name build_vault_deposit, it is immediately distinguishable from build_vault_withdraw, build_vault_top_up and build_curated_vault_deposit.

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?

It implies usage by describing the two deposit modes (USDC-only with an internal swap, or WETH+USDC) and gives concrete minimums, but it never states when to prefer this over siblings like build_vault_top_up (adding to an existing position) or build_curated_vault_deposit, nor when not to use it. Usage is only implied.

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