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

Goes well beyond the annotations: the simulation step, the 'never signs or sends' guarantee, the two distinct return shapes (unsigned tx vs EIP-712 typed data), and the hard failure mode for contract owners are all disclosed. These are exactly the behaviors an agent needs to avoid treating this as a signing tool, and they are consistent with readOnlyHint=true.

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?

Four tight sentences, front-loaded with the action and the return contract, then the branch and the refusal case. No filler and no restatement of the title.

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 and does so by naming both possible payloads. Combined with the threshold branch and the contract-owner refusal, an agent has everything needed to call this correctly or recognize when it will fail.

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 already 100%, so the baseline is 3; the description adds value by explaining that the nested 'approval' object is only used above the threshold and that it carries the owner's EIP-712 signature — the schema states the field shape but not the triggering condition. Minor gap: it doesn't clarify amount precision or market symbol resolution beyond what the schema says.

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 concrete verb+resource ('Add collateral to the account's position') and immediately characterizes the return as UNSIGNED transaction data, which separates it from the read-only siblings like get_position. It doesn't explicitly name the adjacent write siblings (prepare_deposit, prepare_mandate_withdraw_collateral) to route the agent, so differentiation is implied rather than spelled out.

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?

Gives clear conditional guidance: the session-key path is the default, the EIP-712 owner path applies 'above the approval threshold', and the tool 'refuses when the owner is a contract, such as a Safe' — a genuinely useful exclusion. It stops short of naming alternative tools for the Safe/contract case, leaving the agent to infer where to go.

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