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

No annotations are present, so the description carries the behavioral burden. It discloses auth requirements, immediate synchronous return behavior on success, and idempotent retry safety. It does not mention failure modes or financial side effects, but covers the most important operational behavior.

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 concise sentences, each carrying useful information: the action, the prerequisite, the success result, and retry behavior. No filler or redundancy.

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 paid purchase tool with no output schema, the description provides the return expectation and retry semantics. It could be more explicit about failure behavior or the exact response shape, but the schema fully covers parameters and defaults, making the tool callable.

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 baseline is 3. The description adds little beyond the schema—it mentions the API key source and idempotency safety, but these are already captured in the parameter descriptions.

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 action ('Purchase a capability from the marketplace') with a clear resource and verb. It is distinct from read-only siblings like browse_assets, get_asset, and list_asset, and from registration/relay tools.

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: use it to purchase a capability, requires an API key obtained from register_agent, and supports safe retries via idempotencyKey. It does not explicitly name alternatives or exclusions, but the purchase intent and prerequisite are clear.

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