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

The description discloses the x402 payment protocol, the two-phase call pattern, and where the receipt is returned (_meta['x402/payment-response']). It also explains label semantics (omit to keep, empty to clear). Annotations already mark destructiveHint=true, so the 'overwrite' wording is consistent; no contradiction. This adds significant behavioral detail 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?

The description is front-loaded with the core purpose, then details label behavior, payment flow, account requirements, and feedback contact. Each sentence serves a function, and the structure is logical. It is somewhat long but information-dense, so it 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 is paid (x402) and involves a two-phase flow, the description explains how to obtain a quote and complete the operation, including where the receipt is returned. It also notes 'No account, no API key', which are prerequisites. With no output schema, this is reasonably complete for an agent to invoke 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 covers 100% of parameters, so baseline is 3. The description adds meaningful nuance for the 'label' parameter ('Omit label to keep the current one, pass an empty string to clear it'), which is not in the schema. Other parameters (id, plan, contentBase64) are adequately described in the schema, so the description provides incremental value.

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 states a specific verb ('overwrite'), resource ('contents of an object you own'), and scope ('keeping its id, and buy it a fresh plan term'). This clearly distinguishes it from storage_buy (buying a new object) and storage_renew (renewing without replacing content).

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 gives clear context: it is a paid operation with a two-phase payment flow (quote first, then complete), and it explains label behavior and the lack of account/API-key requirements. However, it does not explicitly compare to sibling tools or state when not to use it, so it falls short of a 5.

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