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

Despite readOnlyHint=true, the description adds substantial behavior: checks account limits, returns simulated unsigned transaction data for the session key, returns EIP-712 typed data above the approval threshold, refuses contract owners, and never signs or sends. No contradiction with 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?

Front-loads the core action and conditions, with every sentence carrying operational information. Some domain jargon ('the lag', 'first round') is dense, but the description is appropriately sized for a complex tool.

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?

Covers prerequisites (expiry, lag condition), return behavior (unsigned transaction vs EIP-712 typed data), refusal rules for contract owners, and the no-sign/no-send guarantee. With no output schema, this is complete enough for an agent to call 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?

Schema coverage is 100%, so all five parameters are already documented, including the approval object and sessionKey. The description confirms the conditional role of approval but adds no syntax or format details beyond what the schema provides.

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: prepare a mandate settlement through the account, only after expiry. It explicitly distinguishes itself from the sibling prepare_settle (ordinary wallet), so an agent can select it without opening either schema.

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?

Explicitly says other settlement paths are not agent actions and names prepare_settle for ordinary wallets. Also gives clear when-not conditions: only while the first round landed inside the lag, and it refuses when the owner is a contract such as a Safe.

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