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

With no annotations, the description must disclose side effects itself, and it does: 'Does not move money itself' is a key behavioral caveat, and listing the three returned URL kinds tells the agent what a successful call yields. It could add more about checkout expiration or authorization, but it already covers the most important non-obvious trait.

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?

Three short sentences each carry load: action plus when-to-use, return values, and the non-payment caveat. The main purpose is front-loaded and there is no filler.

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 tool with 13 parameters, no annotations, and no output schema, the description is too thin on invocation details. It explains the return URLs but not what the optional fields mean, when they are required, or what errors or pitfalls exist, so an agent will often have to guess at how to fill the generic fields.

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 only 23%, so the description needed to compensate for the 10 opaque parameters (mc, dot, address, first_time, license_* , etc.). It only reinforces that sku is a SKU and does not explain the other 12 parameters or how they map to different shelf types.

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 opens with a concrete verb and resource: 'Creates a Coinbase checkout for any SKU'. It also gives the tool an explicit identity as an escape hatch and says to use it when no job-named tool exists, separating it from buy_shelf_pass and the other shelf-specific siblings without being tautological.

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?

'Use this when no job-named tool exists' is an explicit routing rule: it tells the agent both when to choose buy_shelf and, by implication, when not to. This is the clearest possible usage guidance for an escape-hatch tool.

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