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

With no annotations, the description bears full responsibility for disclosing behavior. It notably states 'Signs nothing and moves nothing' and emphasizes that Robyn will not hold a balance for a recipient who never consented, which are critical behavioral traits. It does not mention possible errors when nonce retrieval fails or when accounts are not enrolled, but the explicit safety and consent constraints are well covered, justifying a strong score.

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 extremely concise yet information-dense: three sentences cover the exact return value, the workflow (sign and POST), the enrollment prerequisite, and an alternative for unenrolled recipients. There is zero fluff, and the most critical detail (what it returns) is front-loaded. Every sentence earns its place.

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 (simple payload builder with 3 parameters, no output schema) and the rich sibling context, the description is remarkably complete. It explains the return value, the subsequent action required, the enrollment condition, and the alternative route. It effectively differentiates from robyn_netting_enroll_payload and other robyn_* tools without needing to enumerate all siblings.

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 description coverage is 100%, so the schema already documents the parameters. The tool description adds meaningful context beyond this: it clarifies that the 'to' and 'from' must be enrolled accounts, and reveals that the nonce is automatically handled ('with the correct next nonce') and that the final POST includes a 'signature' field, none of which are in the input schema. This enriches the agent's understanding of how the parameters relate in the workflow.

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 function with a specific verb and resource: 'Returns the exact string to sign, with the correct next nonce, for a free instant transfer between two ENROLLED accounts.' It distinguishes itself from siblings by explicitly noting it 'Signs nothing and moves nothing' and by referencing the exact endpoint and POST payload. This makes it unambiguous which action the tool performs.

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 explicit usage context and alternatives: it explains that the sender must sign the returned message and POST it to /api/netting/transfer, and it clearly states the prerequisite that both parties must already be enrolled. It also gives a direct alternative: 'to pay an unenrolled address use the ordinary non-custodial route instead.' This goes beyond merely implying when to use the tool.

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