Build Subscription Transaction

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

Annotations already indicate readOnly/idempotent/non-destructive behavior, and the description adds the key behavioral fact that the returned calldata is signed and sent externally. It also names the exact calldata steps (approve + purchaseSubscription), which is useful beyond 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?

Two concise sentences with no filler. The core purpose is front-loaded, and the build-only behavior is stated immediately after, making the tool's scope immediately clear.

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?

For a calldata-building tool, the description covers the essential behavior: what it builds, what operations are included, and who performs the actual transaction. It does not specify the output format, but the schema and the 'sends it themselves' hint provide enough context for an agent to proceed.

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 already documents all three parameters, including tier pricing and address meanings, so the description adds little parameter-level detail. However, the mention that the sponsor may sign and send provides helpful context for how sponsor_address relates to the transaction flow.

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 uses a specific verb ('Build') and clearly states the resource and action: 'purchase a subscription' via approve(RLC) + purchaseSubscription. This unambiguously distinguishes the tool as a calldata builder rather than a transaction executor.

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 phrase 'The agent (or sponsor) signs and sends it themselves' gives clear usage context: this tool only builds calldata and does not submit transactions. It does not explicitly contrast with sibling tools, but the build-only behavior is stated directly.

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