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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description's 'Does not charge' reinforces that with a useful domain-specific reassurance about money movement. The 'approved agent wallet' phrase hints at an authorization prerequisite, but the description says nothing about what gets persisted, whether the prepared URL expires, or what the returned JSON contains.

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 short sentences with the core action front-loaded and no filler. Brevity is appropriate in form, though here it edges toward under-specification rather than economy.

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 nine-parameter preparation tool with no output schema and no annotation detail about side effects, the description is far too thin — an agent cannot know what the 'exact JSON' is for, what the bound URL resolves to, or how to fill the required scope and disclosure fields. The one-line safety note is helpful but does not compensate for the schema gaps.

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?

The schema has nine parameters at 0% description coverage, including required ones like scope_summary, contact_email, buyer_authorized, and nonconfidential_only, plus optional datasets_before/after, billing_location, and join_key. The description explains none of them — it doesn't even mention the wallet or authorization semantics that buyer_authorized presumably encodes.

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 names a concrete action ('Prepare exact JSON and SHA-256-bound purchase URL') and the target ('for an approved agent wallet'), so an agent can tell this is a checkout-preparation step rather than a charge. It does not, however, distinguish itself from siblings like marketplace_begin_checkout or marketplace_mpp_purchase_instructions, which sound closely related.

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 only usage signal is the embedded precondition 'for an approved agent wallet' and the trailing 'Does not charge', which implies a later charging step exists elsewhere. There is no explicit statement of when to pick this over begin_checkout or mpp_purchase_instructions, and no exclusion guidance.

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