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

Annotations only declare readOnlyHint=false and destructiveHint=false. The description adds significant behavioral context beyond that: it says the batch is unsigned, non-custodial, atomic (EIP-5792/Safe), time-sensitive (meta.expiresAt), and includes a signingUrl for human signing. This enriches the agent's understanding of side effects and constraints without contradicting the annotations.

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 information-dense but not bloated. It leads with the primary purpose, then enumerates the return payload specifics (calls list, preview, signingUrl, expiresAt) and a warning about time-sensitivity. Each sentence contributes to either selection or invocation, though the exact call sequence could be seen as slightly verbose for someone just wanting to know what it does.

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 burden of explaining return values. It covers the main output (calls[] with the explicit sequence), the preview equivalence, the signingUrl, and the expiresAt time-sensitivity. It doesn't detail error conditions or prerequisites, but for a transaction-builder tool this is sufficient for an agent to invoke it correctly.

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?

Input schema coverage is 100% with documented parameter descriptions. The description adds minimal parameter-specific detail; it references strategyId indirectly via 'equity vault' and 'time-sensitive (meta.expiresAt)' relates to the output, not parameters. Since schema already covers parameters fully, the description does not need to duplicate, and a baseline of 3 is appropriate.

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 ('Build') and resource ('UNSIGNED call batch to deposit into a stock + yield equity vault') and clearly differentiates from siblings like build_equity_exit_tx and build_leverage_tx by explicitly scoping to deposit. It also names the output type (calls[]) and the signing context, leaving no ambiguity about what this tool accomplishes.

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?

Implicitly communicates when to use: it says 'for the given wallet to sign' and mentions the preview is the same as simulate_equity_deposit, suggesting the simulation tool is for preview-only. It doesn't explicitly name alternatives or state 'use X instead of Y', but the context is clear enough for an agent to infer the deposit construction use case versus other build tools.

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